More than one version of 'org.apache.commons.logging.Log' visible in the classpath

[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'site'.
[INFO] org.apache.maven.plugins: checking for updates from maven2-repo-dev-java-net
[INFO] org.apache.maven.plugins: checking for updates from maven-repository.dev.java.net
[INFO] org.apache.maven.plugins: checking for updates from hosted.repos
[INFO] org.codehaus.mojo: checking for updates from maven2-repo-dev-java-net
[INFO] org.codehaus.mojo: checking for updates from maven-repository.dev.java.net
[INFO] org.codehaus.mojo: checking for updates from hosted.repos
[INFO] ------------------------------------------------------------------------
[INFO] Building CheckboxTree
[INFO]    task-segment: [site:deploy]
[INFO] ------------------------------------------------------------------------
[INFO] [site:deploy {execution: default-cli}]
WAGON_VERSION: 1.0-beta-2
http://zeus.pin.unifi.it/projectsSites/lablib-checkboxtree_snap - Session: Disconnecting  
http://zeus.pin.unifi.it/projectsSites/lablib-checkboxtree_snap - Session: Disconnected
[FATAL ERROR] org.apache.maven.plugins.site.SiteDeployMojo#execute() caused a linkage error (java.lang.ExceptionInInitializerError) and may be out-of-date. Check the realms:
[FATAL ERROR] Plugin realm = app0.child-container[org.apache.maven.plugins:maven-site-plugin:2.1]
urls[0] = file:/Users/bigagli/.m2/repository/org/apache/maven/plugins/maven-site-plugin/2.1/maven-site-plugin-2.1.jar
urls[1] = file:/Users/bigagli/.m2/repository/org/codehaus/plexus/plexus-utils/1.5.1/plexus-utils-1.5.1.jar
urls[2] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-module-xhtml/1.1.2/doxia-module-xhtml-1.1.2.jar
urls[3] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-core/1.1.2/doxia-core-1.1.2.jar
urls[4] = file:/Users/bigagli/.m2/repository/xerces/xercesImpl/2.8.1/xercesImpl-2.8.1.jar
urls[5] = file:/Users/bigagli/.m2/repository/xml-apis/xml-apis/1.3.03/xml-apis-1.3.03.jar
urls[6] = file:/Users/bigagli/.m2/repository/commons-lang/commons-lang/2.1/commons-lang-2.1.jar
urls[7] = file:/Users/bigagli/.m2/repository/commons-httpclient/commons-httpclient/3.1/commons-httpclient-3.1.jar
urls[8] = file:/Users/bigagli/.m2/repository/commons-logging/commons-logging/1.0.4/commons-logging-1.0.4.jar
urls[9] = file:/Users/bigagli/.m2/repository/commons-codec/commons-codec/1.2/commons-codec-1.2.jar
urls[10] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-module-apt/1.1.2/doxia-module-apt-1.1.2.jar
urls[11] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-module-xdoc/1.1.2/doxia-module-xdoc-1.1.2.jar
urls[12] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-module-fml/1.1.2/doxia-module-fml-1.1.2.jar
urls[13] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-decoration-model/1.1.2/doxia-decoration-model-1.1.2.jar
urls[14] = file:/Users/bigagli/.m2/repository/org/apache/maven/doxia/doxia-site-renderer/1.1.2/doxia-site-renderer-1.1.2.jar
urls[15] = file:/Users/bigagli/.m2/repository/org/codehaus/plexus/plexus-i18n/1.0-beta-7/plexus-i18n-1.0-beta-7.jar
urls[16] = file:/Users/bigagli/.m2/repository/org/codehaus/plexus/plexus-velocity/1.1.8/plexus-velocity-1.1.8.jar
urls[17] = file:/Users/bigagli/.m2/repository/org/apache/velocity/velocity/1.5/velocity-1.5.jar
urls[18] = file:/Users/bigagli/.m2/repository/commons-collections/commons-collections/3.2/commons-collections-3.2.jar
urls[19] = file:/Users/bigagli/.m2/repository/oro/oro/2.0.8/oro-2.0.8.jar
urls[20] = file:/Users/bigagli/.m2/repository/org/apache/maven/shared/maven-doxia-tools/1.2/maven-doxia-tools-1.2.jar
urls[21] = file:/Users/bigagli/.m2/repository/commons-io/commons-io/1.4/commons-io-1.4.jar
urls[22] = file:/Users/bigagli/.m2/repository/org/codehaus/plexus/plexus-archiver/1.0-alpha-7/plexus-archiver-1.0-alpha-7.jar
urls[23] = file:/Users/bigagli/.m2/repository/org/mortbay/jetty/jetty/6.1.5/jetty-6.1.5.jar
urls[24] = file:/Users/bigagli/.m2/repository/org/mortbay/jetty/jetty-util/6.1.5/jetty-util-6.1.5.jar
urls[25] = file:/Users/bigagli/.m2/repository/org/mortbay/jetty/servlet-api-2.5/6.1.5/servlet-api-2.5-6.1.5.jar
[FATAL ERROR] Container realm = plexus.core
urls[0] = file:/Users/bigagli/maven/lib/maven-2.2.1-uber.jar
[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] null
Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed.
[INFO] ------------------------------------------------------------------------
[INFO] Trace
java.lang.ExceptionInInitializerError
	at org.apache.webdav.lib.WebdavSession.getSessionInstance(WebdavSession.java:145)
	at org.apache.webdav.lib.WebdavSession.getSessionInstance(WebdavSession.java:127)
	at org.apache.webdav.lib.WebdavResource.setClient(WebdavResource.java:1273)
	at org.apache.webdav.lib.WebdavResource.setHttpURL(WebdavResource.java:1298)
	at org.apache.webdav.lib.WebdavResource.setHttpURL(WebdavResource.java:1320)
	at org.apache.webdav.lib.WebdavResource.setHttpURL(WebdavResource.java:1408)
	at org.apache.webdav.lib.WebdavResource.<init>(WebdavResource.java:290)
	at org.apache.maven.wagon.providers.webdav.CorrectedWebdavResource.<init>(CorrectedWebdavResource.java:54)
	at org.apache.maven.wagon.providers.webdav.WebDavWagon.openConnection(WebDavWagon.java:143)
	at org.apache.maven.wagon.AbstractWagon.connect(AbstractWagon.java:207)
	at org.apache.maven.wagon.AbstractWagon.connect(AbstractWagon.java:142)
	at org.apache.maven.plugins.site.SiteDeployMojo.execute(SiteDeployMojo.java:212)
	at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:569)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:539)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
	at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
	at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
	at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
	at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
	at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed. (Caused by org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed.) (Caused by org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed. (Caused by org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed.))
	at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
	at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
	at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
	at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
	at org.apache.commons.httpclient.HttpClient.<clinit>(HttpClient.java:69)
	... 31 more
Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed. (Caused by org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed.)
	at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:397)
	at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
	... 35 more
Caused by: org.apache.commons.logging.LogConfigurationException: Invalid class loader hierarchy.  You have more than one version of 'org.apache.commons.logging.Log' visible, which is not allowed.
	at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:385)
	... 36 more
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 19 seconds
[INFO] Finished at: Thu Jan 21 11:52:58 CET 2010
[INFO] Final Memory: 31M/264M
[INFO] ------------------------------------------------------------------------