Still got issues. With 270.41.03 samething. With 270.41.06 behaviour changed - now blackscreen and systemlockup sometimes.
If it'll help, I've managed to get coredumps from xorg with 270.41.03 (execpt around 128k memory region that gdb refused to dump). It's 3.6MB. I've uploaded it to omploader: http://ompldr.org/vOGN5dA