I am also having a problem with debian squeeze X crashes, but only on an x64 system. Nearly identical setup on x32 is working. And it only crashes when using CRT-1 only for output. If I use CRT-0 send to both CRT-0 and CRT-1 it doesn't crash.
http://www.nvnews.net/vbulletin/showthread.php?t=152528