My game crash in showroom too. I think the problem is linked with the online and certain server. I explain:
This weekend i played with my team mate Gaetan. We were on Teamspeack. We joined together a same server (with WTCC 06/07/87 rule), and in the showroom, he selected a custom Alfa 156, and i selected a custom Leon, and we crasched together at the same time. We restarted the game, and the game crashed each time i selected the same skin. But with the default skin, no problem. But sometimes the problem occur with other class (GT pro...).
I hope someone can find what the hell, because it's a very boring problem.
PS: We played with the last steam update.