Mueslo, I seem to have the same problem. I'm running a Debian/testing with a HD7970. The problem arises even with the latest fglrx version (19 december), mostly when I EVA (there's something like a 75% chance an EVA will freeze X). X is then unkillable, and KSP.x86_64 as well. It seems to occur with the 32bit KSP version as well. I've tried many things to avoid that, no to avail. Latest fglrx, 32 bits KSP version, AMD compatibility mode (seems to be a CPU related fix, but hey.) If someone's got news about this ...