Okay, I hope I don`t annoy anyone but I could not find my problem in a thread here...
I played my game yesterday and all worked as usual.
Today, I started my pc and wanted to load the game but it didn`t start. There popped up an error message but it containes no information (I added a little picture of it).
I did not add any CC or changed anything about the game. But in case it should be a CC problem, I removed my downloads folder and tried to start the game - but the error message popped up again.

I didn`t want to lose everything by re-installing the game, so I tried one last thing: We have different Windows users on one pc and I tried to start the game at my brother`s account - and there it worked without problems!

This is really weird and I just can`t think of anything that could cause the problem. Perhaps some of you have some ideas what could have went wrong with the game or my pc...
It would be very nice if somebody could help me.

*attached image removed*