I'm using the True AI mod and the mod manager. My saved game works fine and I can save fine. I don't see much of a difference from the stock game TBH but the changes are meant to be subtle. I've only done 1 race and a practice session with the mod also.
Protege- try to uninstall all mods and install them one-by-one, testing o see if you save each time. and you will find out which mod(s) is the culprit.