What version of the Simple GA mod are you using? I've seen this happen when you try to install a module (any mod) and it 'fails' (usually the first time) then you try to reinstall but not all of the items from the prior install (database entries) are removed / or the configuration ids are mixed up from that install.

On this site in question, did you have another version of GA already installed when you tried to install this one?

Let me know on those and I'll see what I can do to help you work through it. In the worst case senerio you can go into phoMyAdmin and manually remove the entries for the mod then reinstall from the SQL patch in the zen admin to get that to work.

No need to remove files--just the db entries.