Quick easy painless fix:
In the address bar of your browser type {your-url}/modules/system/admin.php?fct=groups&op=modify&g_id=1
(I recommend C&P the above and insert your XOOPS URL -- http://www.zobot.net/modules/system/admin.php?fct=groups&op=modify&g_id=1 maybe?)
Now select every check box to give the Webmaster group access to every "System Admin rights"
Now click "Update Group" and voila! Everything should be back to normal now.