error when trying to create new usergroup

[ravelinks]

We have 3.8.0/b1, and when attempting to create a new usergroup (add new usergroup in the admin control panel), we get the following message when trying to save the new usergroup:

Fatal error: Call to a member function on a non-object in /home/www/ravelinks/forums/admincp/usergroup.php on line 492

[Floris]

3.8 is in beta and unsupported. Reupload the files and disable the hook system, and try again. Run diagnostics > file suspect to try and see if any file is mismatching.
And make sure the upgrade.php script has completed.

If it still happens, check the bug tracker and see if it is a known bug, otherwise submit it as one.