What I've found is this:
-With in-game AA settings set to "on" and ATI's control panel AA settings set to override the game's settings, I get the awful graphics shown above.
-With the in-game AA settings set to "on" and ATI's control panel AA settings set to use the in-game settings, only the map labels and the "move/assault/etc. panel at the bottom have the "purple graphics" problem.
-With the in-game AA settings set to "off" and ATI's control panel AA settings set to "use in-game settings" I don't have any corrupted graphics, but of course the game looks ugly (but playable) with all those jagged edges.
I should add the video card is very new, not overclocked, and running on the latest Catalyst drivers. No problems like this show up in any of my other games.