The problem appears due to hibernate consuming a lot of perm gen! It should be in a wiki, release note, documentation - or even set by default - but it is not :-( To fix MaxPermSize : in jboss server, customize the "run.bat" file set JAVA_OPTS=%JAVA_OPTS% -Xms512m -Xmx1274m -XX:MaxPermSize=256m -Dcom.sun.management.jmxremote To fix it within eclipse, use 3.3.1 or above, and customize the eclipse.ini file to include something like that -showsplash org.eclipse.platform --launcher.XXMaxPermSize 256m -vmargs -Xms40m -Xmx512m View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4137915#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...