I installed 1.6beta3 on my laptop last night.  While doing some 
disk-intensive stuff, X froze.  The machine itself was still alive -- I 
was able to login in remotely -- but I couldn't get anything X-related 
to respond.  Killing twm, and even killing X, didn't help -- they 
exited, but the scren and keyboard appeared to be frozen.  I eventually 
had to reboot.

I'm running X 4.1.0 on a Thinkpad T21, if that helps.  It's using the 
Savage driver.

		--Steve Bellovin, http://www.research.att.com/~smb (me)
		http://www.wilyhacker.com ("Firewalls" book)