I took a kind of shotgun effect to looking at the problem. I found the libgsm file online (it's a .dsc file and I didn't bother looking up what it is). Just for giggles, I put a copy in the Extraction Point folder and another copy in the crossover games contents (right click app and 'show contents'), and put it in sharedsupport/crossovergames/lib. Then I simply turned down the settings on the game (which I'm 99% certain why I've just played for a while with no problems at all).
If anybody gets the same crashing effect, I'd recommend first just lowering the performance options on the game and then, if that doesn't work, try putting the libgsm file, first in the Extraction Point folder, and if that doesn't work, then in the crossovergames contents. As I said, I'm pretty sure I just needed to turn down the settings a bit.