JBoss changed its Repository URL, so our Nexus Repository Manager was not able to download the newest Hibernate Version (3.5.1-Final). Although the old JBoss Repository is readable and searchable we had problems downloading the .jar files. We changed the URL to the new JBoss Repository URL and everything worked fine again.

This is the new URL:

https://repository.jboss.org/nexus/content/groups/public