Cannot create new group (http status code 500)

Steps to reproduce:

1. Installed the application on Centos with glassfish 4.1 with postgres 9.2.x, sun jdk 1.8.
2. Altered hibernate.cfg.xml to use postgres, commented out hsqldb xml.
3. Ran distribution wizard.
4. Navigated to groups admin page x.x.x.x:8080/xwiki/bin/admin/XWiki/XWikiPreferences?section=Groups
5. Entered name "XWikiNewGroup" for the new group and clicked Create group.

In developer tools in my browser I get error 500 for GET http://x.x.x.x:8080/xwiki/rest/wikis/xwiki/spaces/XWiki/pages/XWikiNewGroup

Have you heard of this? or do you know what classes I should enable in logback.xml to find out more info?

Thanks.