Thanks Pam. I restarted the game many times but it didn't seem to help. I am glad that it is working now though! I play in full screen, so maybe I'll try windows mode if this happens again. I have just found in the past that tabbing out of the game and back into it (with the windows key) can play havoc with the game and make it crash, so that would be my main worry with windows mode. But thanks for the suggestion! I'm very glad to have found such a quick solution!