I'm seeing the same issue with X.Org Version 1.7.1 and the latest NVIDIA drivers whenever I try using Xinerama.
Case 1) If I turn off Xinerama in the xorg.conf and use separate X displays or Twinview, everything works.
Case 2) If I set Xinerama on in xorg.conf, the mouse starts bouncing weird if I try to go to screen two, and if I sit there and scratch my head for a second I get dumped back to the prompt with a segfault.
I'm using a pair of 8800GT's and an 8400GS in this computer.
Originally Posted by David Ronis
I just installed 190.42 and started X. Everything seems fine as far as the graphics image is concerned; however, the mouse doesn't work on the second screen. Mousing there loses control of the mouse (key clicks don't work, position jumps around more or less randomly, cursor flickers) and after a while X crashes.
I'm running the git master (as of last week or so) of X, but this has been a recurring problem with the last several 190.xx drivers. Xinerama used to work with this system.
I've attached the output of nvidia-bug-report.