by juice masters.
I tried the 2.2.6 -> 2.6 upgrade again and just for fun I tried renaming the problem tables (ie.'grading1'). The upgrade finished but I got another error saying "Installation must be finished from the original IP address, sorry." This is even more confusing because unless the IP address is stored in the quiz reports table I wouldn't expect this error. The cofig file is setup as it should be.