I couldn't find many hits at all for this issue.

I'm not getting much apart from the dump; no 'general protection fault'.  But since I upgraded a machine to 9.04 and piled on a bunch of upgrades and additions, every time I've shut down the gnome session has ended, screens gone blank, system beeps, and hangs.  I can't get to a virtual terminal. Numlock still responded, so I concluded it was a UI problem. 

I can ssh in from another system and interact in a limited fashion; 'ps' hangs. init 0 does nothing; poweroff -f worked the first time, but not the second.

I'm running the nvidia driver offered by ubuntu.

 2.6.28-11-generic #42-Ubuntu SMP

first time ..

May 31 21:57:46 akira kernel: [ 2820.596735] NFSD: starting 90-second grace period
May 31 22:11:22 akira -- MARK --
May 31 22:21:23 akira kernel: [ 4237.473900] Dumping ftrace buffer:
May 31 22:21:23 akira kernel: [ 4237.473940]    (ftrace buffer empty)
May 31 22:21:23 akira kernel: [ 4237.473978] CPU 3 
May 31 22:21:23 akira kernel: [ 4237.474048] Modules linked in: nfsd auth_rpcgss exportfs nfs lockd nfs_acl sunrpc binfmt_misc bridge stp bnep video output input_polldev lp snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss tvaudio snd_seq_midi snd_rawmidi bttv snd_seq_midi_event ir_common compat_ioctl32 videodev v4l1_compat i2c_algo_bit snd_seq snd_timer snd_seq_device v4l2_common videobuf_dma_sg iTCO_wdt videobuf_core snd iTCO_vendor_support btcx_risc psmouse soundcore ppdev tveeprom pcspkr serio_raw snd_page_alloc e752x_edac shpchp parport_pc parport edac_core nvidia(P) reiserfs usbhid ohci1394 e1000 ieee1394 mptspi mptscsih mptbase scsi_transport_spi floppy raid10 raid456 async_xor async_memcpy async_tx xor raid1 raid0 multipath linear fbcon tileblit font bitblit softcursor
May 31 22:21:23 akira kernel: [ 4237.476914] Pid: 11255, comm: usplash Tainted: P           2.6.28-11-generic #42-Ubuntu
May 31 22:21:23 akira kernel: [ 4237.476957] RIP: 0010:[<ffffffff80239290>]  [<ffffffff80239290>] reserve_memtype+0x3f0/0x640
May 31 22:21:23 akira kernel: [ 4237.477040] RSP: 0018:ffff88012c903d18  EFLAGS: 00010286
May 31 22:21:23 akira kernel: [ 4237.477080] RAX: 0000000010000000 RBX: 000ffffffffffff0 RCX: ffff88012c903d78
May 31 22:21:23 akira kernel: [ 4237.477123] RDX: ffffffffffffffff RSI: 000000000fff0000 RDI: ffffffffffff0000
May 31 22:21:23 akira kernel: [ 4237.477171] RBP: ffff88012c903d58 R08: 00000000000000fb R09: 0000000000000000
May 31 22:21:23 akira kernel: [ 4237.477217] R10: ffff8801138fc1f8 R11: 00000000000000a8 R12: ffffffffffff0000
May 31 22:21:23 akira kernel: [ 4237.477265] R13: ffffffffffff0000 R14: ffffffffffffffff R15: ffff88012c903d78
May 31 22:21:23 akira kernel: [ 4237.477313] FS:  00007f4578ff46f0(0000) GS:ffff88012f286180(0000) knlGS:0000000000000000
May 31 22:21:23 akira kernel: [ 4237.477368] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 31 22:21:23 akira kernel: [ 4237.477414] CR2: 00007f4578b8c4af CR3: 000000011d508000 CR4: 00000000000006a0
May 31 22:21:23 akira kernel: [ 4237.477462] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
May 31 22:21:23 akira kernel: [ 4237.477503] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
May 31 22:21:23 akira kernel: [ 4237.477503] Process usplash (pid: 11255, threadinfo ffff88012c902000, task ffff88011c540000)
May 31 22:21:23 akira kernel: [ 4237.477503]  ffffe200040563f8 000000000fff0000 ffff88011d5087f0 000ffffffffffff0
May 31 22:21:23 akira kernel: [ 4237.477503]  RSP <ffff88012c903d18>
May 31 22:21:23 akira kernel: [ 4237.481222] ---[ end trace fbfc36c66025a970 ]---
May 31 22:29:43 akira syslogd 1.5.0#5ubuntu3: restart.
May 31 22:29:43 akira kernel: Inspecting /boot/System.map-2.6.28-11-generic

[poweroff -f followed]

May 31 22:29:51 akira kernel: [   69.933092] ADDRCONF(NETDEV_UP): eth0: link is not ready
May 31 22:29:51 akira kernel: [   69.957666] e1000: eth0: e1000_watchdog: NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
May 31 22:29:51 akira kernel: [   69.958976] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
May 31 22:30:29 akira kernel: [  108.606293] Dumping ftrace buffer:
May 31 22:30:29 akira kernel: [  108.606332]    (ftrace buffer empty)
May 31 22:30:29 akira kernel: [  108.606370] CPU 3 
May 31 22:30:29 akira kernel: [  108.606440] Modules linked in: nfs binfmt_misc bridge stp bnep nfsd lockd nfs_acl auth_rpcgss sunrpc exportfs video output input_polldev lp snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi tvaudio snd_seq_midi_event bttv ir_common compat_ioctl32 snd_seq videodev v4l1_compat i2c_algo_bit snd_timer v4l2_common snd_seq_device iTCO_wdt iTCO_vendor_support ppdev videobuf_dma_sg videobuf_core snd parport_pc psmouse btcx_risc tveeprom soundcore e752x_edac pcspkr serio_raw snd_page_alloc shpchp parport edac_core nvidia(P) reiserfs usbhid ohci1394 ieee1394 e1000 mptspi mptscsih mptbase scsi_transport_spi floppy raid10 raid456 async_xor async_memcpy async_tx xor raid1 raid0 multipath linear fbcon tileblit font bitblit softcursor
May 31 22:30:29 akira kernel: [  108.609324] Pid: 4735, comm: usplash Tainted: P           2.6.28-11-generic #42-Ubuntu
May 31 22:30:29 akira kernel: [  108.609368] RIP: 0010:[<ffffffff80239290>]  [<ffffffff80239290>] reserve_memtype+0x3f0/0x640
May 31 22:30:29 akira kernel: [  108.609451] RSP: 0018:ffff88012452bd18  EFLAGS: 00010286
May 31 22:30:29 akira kernel: [  108.609492] RAX: 0000000010000000 RBX: 000ffffffffffff0 RCX: ffff88012452bd78
May 31 22:30:29 akira kernel: [  108.609534] RDX: ffffffffffffffff RSI: 000000000fff0000 RDI: ffffffffffff0000
May 31 22:30:29 akira kernel: [  108.609583] RBP: ffff88012452bd58 R08: 00000000000000fb R09: 0000000000000000
May 31 22:30:29 akira kernel: [  108.609629] R10: ffff88012c41fa80 R11: 00000000000000a8 R12: ffffffffffff0000
May 31 22:30:29 akira kernel: [  108.609675] R13: ffffffffffff0000 R14: ffffffffffffffff R15: ffff88012452bd78
May 31 22:30:29 akira kernel: [  108.609695] FS:  00007fef5c2326f0(0000) GS:ffff88012f286180(0000) knlGS:0000000000000000
May 31 22:30:29 akira kernel: [  108.609695] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 31 22:30:29 akira kernel: [  108.609695] CR2: 00007fef5bdca4af CR3: 0000000124d7d000 CR4: 00000000000006a0
May 31 22:30:29 akira kernel: [  108.609695] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
May 31 22:30:29 akira kernel: [  108.609695] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
May 31 22:30:29 akira kernel: [  108.609695] Process usplash (pid: 4735, threadinfo ffff88012452a000, task ffff880126182cc0)
May 31 22:30:29 akira kernel: [  108.609695]  ffffe20003ff4eb0 000000000fff0000 ffff880124d7d7f8 000ffffffffffff0
May 31 22:30:29 akira kernel: [  108.609695]  RSP <ffff88012452bd18>
May 31 22:30:29 akira kernel: [  108.613628] ---[ end trace 50076a3be29e93e4 ]---
Jun  1 20:27:48 akira syslogd 1.5.0#5ubuntu3: restart.
Jun  1 20:27:48 akira kernel: Inspecting /boot/System.map-2.6.28-11-generic

[had to power down the system]

Xorg.0.log attached as requested for previous submitter.  Please let me know what other data you need.