[otrs] 'Admin' rights gone for all accounts

A few weeks ago I went on vacation, and when I came back someone had (somehow) removed all access to the admin functions from everyone (including root). I have access to the database, and I can log into the system from the front end. It looks like I'm still a member of the Admin group, but the "Admin" butting is missing and even trying action=Admin gets me a "no permissions" error. I can't find any place in the database that assigns group permissions to modules or functions, so I can't see any method for reversing this and getting control of my system back. Anyone have any suggestions? Richard A. Obenchain