After installing the Catalyst 13.1 driver, Team Fortress 2 now runs for my Radeon HD 4850 in Kubuntu 12.04 x64. Trying to enable MSAA, however, causes the game to crash, and attempting to restart under these conditions produces a black screen with the following error in a window:
Failed to create OpenGL device!
Please see the following for more info.
Said link is irrelevant to me, since it refers to something specific to DirectX, but maybe it'll shed some light on what's going wrong to the driver's developers. After manually deleting the file that stores the graphics settings for the game, it started up properly again. I don't know if you have any idea what OpenGL functions are used to enable MSAA in that game, but they must be different from the ones Half-Life use, because that game has AA on by default for some reason and runs just fine.