I also had the problem that the game kept crashing after some sort of ?steam update?. Today I thought about another try with a different approach. Steam often recommends to check the integrity of the game files when problems occur. So I did the check, resulting in a 5.3MB large file download from steam for JC2. After installation the trainer and the game are working together again.
So for all of you where the game in connection with the latest trainer is crashing try the above. Working here.