Well, I upgraded from Nvidia 8600 to an ATI 4850, so i reinstalled the game, then installed the 1.0 patch from here, then the graphics patch from here, set it at 1280x1024 and ---- ta da - the game works! Look through this thread and you'll see I had all sorts of grief with my nvidia card, trying all sorts of things.
The best I could manage was software mode using a slowdown utility (see above!). Now with an ATI card I need no slowdown software or anything, and the game (well the text especially!) looks fantastic! Now all I have to do is start learning to play the game and survive until my team has levelled up a bit!!!