X hangs in mysterious ways

[Simon Law <sfllaw@engmail.uwaterloo.ca>]

Hello,

	I seem to have a small, and mysterious problem.

	I am running Sid with XFree86 4.0.3-3 on Linux 2.4.4.  My 
predicament, you see, is that my X server seems to hang the machine
whenever it fancies.  I have maximum uptimes of about 15 to 20 minutes
of usage.  If I don't touch my X server, it's fine.  If I don't use
my X server, it's fine.  I've tried MemTest86, but that passed with
flying colours.  Any suggestions for log files to look at, or diagnostics
to run?

Simon