It looks like you have installed an unofficial game modification that does not match your current version of The Sims 3.

It looks like you have installed an unofficial game modification that does not match your current version of The Sims 3. We recommend that you either uninstall these game modifications or get updated versions of them - otherwise you may experience crashes.

I had all expansions but the master suite and showtime installed. I installed them both and updated the game, then I got this message. I saw the response to one user was to move the documents/eagames/thesims3 folder to the desktop and tried that. This got rid of the message but I used all package files which were deleted for my cc, which there is an extensive amount of. All of the cc was fixed after the pets bug and I have no mods. What do I do now?

//EDIT

I've done a bit of playing around. I don't think its a bad mod or cc because if I only put one download in and try to install it, I get the message again with various only one piece of cc. So it seems like a game problem.