We have been running a course in Moodle 1.9.5 (Build:20090513)and everything was working fine. Then suddenly today I got an email from a student who was doing their quiz and submitting it but it would just take them back to the quiz again upon submission and was not recording the grade. I have tried logging in as other users and get the same results and tried it on multiple browsers and still same thing. I checked the database quiz tables, optimized, repaired, etc. it all said they were ok. I am not sure what else to try in order to fix this as it is now holding up about a dozen students and we have new ones coming in weekly. Any help would be greatly appreciated.
Well computers are (supposedly) deterministic. So, something must have changed to trigger the change in behaviour. You need to do some detective work to find out what.