window managers crashing

It's difficult to say, but I believe after updating the system recently is when I started having this problem. I logged out as one user in gnome, then logged in as another in xfce. All seemed well until I logged out of xfce and back into gnome. X crashed and things haven't worked normally since. gdm will work, but when logging in gnome hangs before the splash screen. Putting an entry into .xinitrc allows me to startx and use either wmaker or blackbox. xfce crashes hard.

Here is some output from /var/log/messages when trying to use gnome:

Nov 25 19:58:57 katlian kernel: [ 55.408811] nm-applet[7214]: segfault at 00002abf84925eff rip 00002abf0f6965b0 rsp 00007fffa2579278 error 4
Nov 25 19:58:57 katlian kernel: [ 55.500253] gnome-panel[7160]: segfault at 00002ad3201136ff rip 00002ad2b57c85b0 rsp 00007ffff9541f08 error 4
Nov 25 19:58:59 katlian kernel: [ 57.844126] gnome-panel[7263]: segfault at 00002b593df23068 rip 00002b5933a327d9 rsp 00007fff78a5a430 error 4
Nov 25 19:59:00 katlian kernel: [ 58.065828] gnome-panel[7266]: segfault at 00002af7682a3068 rip 00002af75ddb27d9 rsp 00007fff4e6da0b0 error 4
Nov 25 19:59:00 katlian kernel: [ 58.296406] gnome-panel[7270]: segfault at 00002b0697969068 rip 00002b068d4787d9 rsp 00007fff1f0159f0 error 4
Nov 25 19:59:00 katlian kernel: [ 58.508678] gnome-panel[7273]: segfault at 00002af4d832a068 rip 00002af4cde397d9 rsp 00007fffde653030 error 4
Nov 25 19:59:00 katlian kernel: [ 58.747102] gnome-panel[7276]: segfault at 00002b4fa49ce068 rip 00002b4f9a4dd7d9 rsp 00007fff11fb1980 error 4
Nov 25 19:59:01 katlian kernel: [ 58.994271] gnome-panel[7289]: segfault at 00002b0d27d69068 rip 00002b0d1d8787d9 rsp 00007fff8ec145f0 error 4
Nov 25 19:59:01 katlian kernel: [ 59.070996] update-notifier[7193]: segfault at 00002b52cd457bc0 rip 00002b52c46767d9 rsp 00007fffe9246190 error 4
-truncated-

This happens whether I use kernel 2.6.22-14-xen or kernel 2.6.22-14-generic.

I wonder if this might be related to using envy, though I had used it without problems for the better part of the month. In /var/log/Xorg.0.log, an error shows:

(EE) Failed to initialize GLX extension (Compatible NVIDIA X driver not found)

However, I am using the generic nv driver since having problems with X. My video card is a GeForce 7900 GS. I'm using ubuntu 7.10 amd64. My processor is an amd 64bit 5000+. Memory is currently 4gb.