Not authorized to use method with version parameter

I have instantiated an xml-rpc client in php (which is working) with login / password of archiva administrator account.

But I have a strange behavior.

According to this documentation :
http://archiva.apache.org/docs/1.2.1/adminguide/web-services.html

I can use Administration Service, and get back information.

I can use Search Service, excepted methods that are using a version of artifact in parameter!

For example :

SearchService.getArtifactVersions( String groupId, String artifactId ) is working
AdministrationService.getAllManagedRepositories() is working

SearchService.getDependencies( String groupId, String artifactId, String version ) is not working, And the returned message is : "Not authorized".
SearchService.getDependencyTree( String groupId, String artifactId, String version ) is not working, And the returned message is : "Not authorized".

I don't understand my mistake because there is no problem with administration Service which needs an user with System Administrator role in Archiva, but it is not working for Search Services with an artifact version, which needs only an user with at least a Repository Observer role. So for me it's a bug