I've repeatedly found that the framebuffer in X gets corrupted. 
Sometimes the screen appears to wrap in such a way that I can see the 
mouse pointer in two places on the screen, but the colors are all wrong 
and there are chunks missing.  This has happened with 1.6.1, 1.6.2, and 
2.0 on this machine (with the same video card).  It usually is after 
mplayer or when coming back from the screensaver), and the only way to fix 
it is usually to Ctrl-Alt-F2 to a virtual console and then go back via 
Ctrl-Alt-F1.  Sometimes it happens after the screensaver (just a normal 
xset s on; xset s 200 (no OpenGL screensavers)).

After it has happened twice I often can't change to the virtual console 
via the keyboard.  When this happens I also find that if I type "halt" in 
an xterm some visible apps change, but it still appears as if X is running 
even though it isn't (the mouse pointer is visible but doesn't move).  At 
first I thought it was a lockup, but if I wait long enough it umounts the 
disks and when I reboot the disks are clean.

A few bits from my dmesg:
  vga1 at pci1 dev 0 function 0: Nvidia Corporation GeForce2 MX (rev. 0xb2)
  wsdisplay0 at vga1 kbdmux 1: console (80x25, vt100 emulation)
  wsmux1: connecting to wsdisplay0
  wsdisplay0: screen 1 added (80x25, vt100 emulation)


I'm not always able to duplicate the problem.  Is there a way to torture 
test X for bugs like this?

I'm planning to rebuild the kernel with XSERVER_DDB, and try to hit F12 
when it happens next.  What should I look for in the dump?  Is there a 
better method?


Thanks,

George