X fails to start (segfault) after upgrade to Oneiric

X no longer launches after upgrading a 64-bit Mythbuntu install from 11.04 to 11.10.

Output of lspci -nn | grep VGA:
00:05.0 VGA compatible controller [0300]: nVidia Corporation C51PV [GeForce 6150] [10de:0240] (rev a2)

Packages:
linux-image-3.0.0-12-generic
nvidia-current (280.13-0ubuntu6)

End of /var/log/Xorg.0.log:
[ 868.341] (**) NVIDIA(0): DPI set to (100, 100); computed from "DPI" X config option
[ 868.341] (**) NVIDIA(0): Enabling 32-bit ARGB GLX visuals.
[ 868.341] (--) Depth 24 pixmap format is 32 bpp
[ 868.341] [ 868.342] [ 868.348] [ 868.348] [ 868.349] (II) NVIDIA(0): Setting mode "1366x768a50"
[ 868.461] [ 868.465]
Backtrace:
[ 868.465] 0: /usr/bin/X (xorg_backtrace+0x26) [0x460576]
[ 868.465] 1: /usr/bin/X (0x400000+0x64b8a) [0x464b8a]
[ 868.465] 2: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7fa9ff957000+0x10060) [0x7fa9ff967060]
[ 868.465] 3: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0x46d7b9) [0x7fa9fa48f7b9]
[ 868.465] 4: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0xc9fb7) [0x7fa9fa0ebfb7]
[ 868.465] 5: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0xca1c9) [0x7fa9fa0ec1c9]
[ 868.465] 6: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0x85dad) [0x7fa9fa0a7dad]
[ 868.465] 7: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0x7e090) [0x7fa9fa0a0090]
[ 868.465] 8: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0xe9553) [0x7fa9fa10b553]
[ 868.465] 9: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0xab8c6) [0x7fa9fa0cd8c6]
[ 868.465] 10: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0xb0926) [0x7fa9fa0d2926]
[ 868.465] 11: /usr/lib/x86_64-linux-gnu/xorg/extra-modules/nvidia_drv.so (0x7fa9fa022000+0x42df88) [0x7fa9fa44ff88]
[ 868.465] 12: /usr/bin/X (AddScreen+0x171) [0x42fed1]
[ 868.465] 13: /usr/bin/X (InitOutput+0x29c) [0x473bac]
[ 868.465] 14: /usr/bin/X (0x400000+0x23143) [0x423143]
[ 868.465] 15: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xed) [0x7fa9fe89330d]
[ 868.465] 16: /usr/bin/X (0x400000+0x235ed) [0x4235ed]
[ 868.466] Segmentation fault at address 0x240
[ 868.466]
Caught signal 11 (Segmentation fault). Server aborting
[ 868.466]
Please consult the The X.Org Foundation support
         at http://wiki.x.org
 for help.
[ 868.466] Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 868.466]
[ 868.478] ddxSigGiveUp: Closing log