@urith with me the screen just freezes ingame and I don't get a black screen.. One time my pc just rebooted while in the game it was shocking really..
But I just bought a new graphics and I have excactly the same problems with my Gigabyte GTX660 OC.
GTX275 still rules gonna sell it.
Wish I could sell Simcity tbh. Very frustrating and it might even be bad for my hardware if it makes my pc reboot.
You really shouldn't release a game when it's not finished. This kind of things should happen in a beta version.