I found the cause of this error, the game crashed because I had a browser window open in the background, maybe flashplayer is the actual cause since I had a youtube tab on. I have never had this problem with a game before and I often run something on my second monitor while playing.
Hopefully a dev sees this so this problem can be dealt with, it did definately not occur when I last played Train Fever which was about 3 months ago. So it has to be a problem with the patches that were released since then.