Invalid field error with no field name on save options attempt in backend

I just installed Quick2Cart. Was able to edit and save the Options once. Now when I try to save (or even cancel) out of the Options page for it, I get "Invalid field:" with no field name or anything or any other error message, and cannot save the options. Haven't done anything unusual and even tried changing the fields I'd changed back to normal. Not running an ad blocker or anything.