Exceptions are not throw

I cant see the stack trace of the generated exception, is not generated in te application server log and the browser returns
<?xml version='1.0' encoding='UTF-8'?><error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"><code/><message xml:lang="en-US">An exception occurred.</message></error>

This happen when i request the URL: http://localhost:8888/odata/