Can't access usergroup manager in AdminCP anymore

[tobias_t]

Hello,

For several weeks now, I have been unable to access the four first entries in the "Usergroups" tab in AdminCP anymore - basically all links that refer to /usergroup.php are dead.

I tried it on several browsers from several computers, but all these four entries only bring up a white page in the AdminCP frame without even so much as an error message.

Any help here would be tremendously appreciated!

Thanks, Tobias