Patched ET to 2.56. And it still runs great with this configuration. No texture artifacts.
Don't know what else to suggest.
But, I noticed that you installed the driver using RPM's, and the Mesa stuff has to be removed to install it. (Else you get conflicts). I still have them installed. Mainly due to the fact that some of the GL games still require them. And if I remove the Mesa files, they no longer run. (Possibly due to them using the SDL stuff, which I think has something to do with it I guess).