Multiplayer : Not Compatible

I am not new to the game, I have been playing since release. However, every so often, about once every two days, my Multiplayer comes up with "not compatible". Now, I do have the 1.1 patch, have managed to play about 20-30 games... So whats going on?

When it has done this before I usually just re-install, which is what I did this time but had to do it twice... Which, I know it's a solution but it's not good enough... And is getting very frustrating....

I was wondering whether anyone else gets this problem often? And if they have managed to find a decent solution.

Thanks

do you get not compatible on certain games or does it pop up as an overall message for all the games in the lobby. If it's just certain games, they're probably playing a mod, if it's all games are you sure you haven't modded the game at all? Maybe changed or deleted something by accident?

Who ever you are playing, could also be cheating. Elmo says he's encountered people with greek units in a roman army and all sorts of mis matches. People are able to mess with the units and factions and still join games, it will desych later though. Anyways just a thought.

Crom