Here is the syslog part from the time of reboot (that failed): 
May 12 11:35:59 pansen x-session-manager[3621]: WARNING: Client '/org/gnome/SessionManager/Client10' failed to reply before timeout 
May 12 11:36:10 pansen kernel: [ 4866.200006] BUG: soft lockup - CPU#0 stuck for 61s! [master:2995]
May 12 11:36:10 pansen kernel: [ 4866.200008] Modules linked in: hidp binfmt_misc ppdev bridge stp bnep input_polldev lp parport joydev snd_hda_intel arc4 ecb snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss iwlagn iwlcore snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device thinkpad_acpi pcmcia mac80211 led_class iTCO_wdt video psmouse snd soundcore btusb iTCO_vendor_support nvram output intel_agp pcspkr snd_page_alloc cfg80211 yenta_socket rsrc_nonstatic pcmcia_core serio_raw nvidia(P) e1000e vesafb fbcon tileblit font bitblit softcursor
May 12 11:36:10 pansen kernel: [ 4866.200008] CPU 0:
May 12 11:36:10 pansen kernel: [ 4866.200008] Modules linked in: hidp binfmt_misc ppdev bridge stp bnep input_polldev lp parport joydev snd_hda_intel arc4 ecb snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss iwlagn iwlcore snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device thinkpad_acpi pcmcia mac80211 led_class iTCO_wdt video psmouse snd soundcore btusb iTCO_vendor_support nvram output intel_agp pcspkr snd_page_alloc cfg80211 yenta_socket rsrc_nonstatic pcmcia_core serio_raw nvidia(P) e1000e vesafb fbcon tileblit font bitblit softcursor
May 12 11:36:10 pansen kernel: [ 4866.200008] Pid: 2995, comm: master Tainted: P           2.6.28-12-generic #43-Ubuntu
May 12 11:36:10 pansen kernel: [ 4866.200008] RIP: 0010:[<ffffffff8041fa95>]  [<ffffffff8041fa95>] __read_lock_failed+0x5/0x20
May 12 11:36:10 pansen kernel: [ 4866.200008] RSP: 0018:ffff880139555d50  EFLAGS: 00000297
May 12 11:36:10 pansen kernel: [ 4866.200008] RAX: ffff880139d28000 RBX: ffff880139555d58 RCX: ffff880139555e38
May 12 11:36:10 pansen kernel: [ 4866.200008] RDX: 0000000000000101 RSI: ffff8801260a3000 RDI: ffff880139ce02c4
May 12 11:36:10 pansen kernel: [ 4866.200008] RBP: ffff880139555d58 R08: 0000000000000000 R09: ffff8801190b4f00
May 12 11:36:10 pansen kernel: [ 4866.200008] R10: 0000000000000000 R11: 0000000000000246 R12: ffff880028030970
May 12 11:36:10 pansen kernel: [ 4866.200008] R13: ffff880139d28038 R14: 000000000000000c R15: 0000000000000000
May 12 11:36:10 pansen kernel: [ 4866.200008] FS:  00007f1ee17b06f0(0000) GS:ffffffff80a9a000(0000) knlGS:0000000000000000
May 12 11:36:10 pansen kernel: [ 4866.200008] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
May 12 11:36:10 pansen kernel: [ 4866.200008] CR2: 00000000045f9840 CR3: 00000001398bb000 CR4: 00000000000006a0
May 12 11:36:10 pansen kernel: [ 4866.200008] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
May 12 11:36:10 pansen kernel: [ 4866.200008] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
May 12 11:36:10 pansen kernel: [ 4866.200008] Call Trace:
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff80699cff>] ? _read_lock+0xf/0x20
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802f39a0>] do_path_lookup+0x50/0x200
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff803d0821>] ? security_file_alloc+0x11/0x20
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802f3c25>] path_lookup_open+0x65/0xd0
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802f4b39>] do_filp_open+0xb9/0x930
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8025c73a>] ? del_timer_sync+0x1a/0x30
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8069858a>] ? schedule_timeout+0x6a/0xd0
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8025c220>] ? process_timeout+0x0/0x10
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8022f669>] ? default_spin_lock_flags+0x9/0x10
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8041fe4c>] ? strncpy_from_user+0x4c/0x80
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff80699e69>] ? _spin_lock+0x9/0x10
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802ff0b1>] ? alloc_fd+0x121/0x150
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802e5711>] do_sys_open+0x81/0x150
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff802e580b>] sys_open+0x1b/0x20
May 12 11:36:10 pansen kernel: [ 4866.200008]  [<ffffffff8021253a>] system_call_fastpath+0x16/0x1b
May 12 11:36:22 pansen console-kit-daemon[3042]: GLib-GObject-WARNING: IA__g_object_get_valist: value location for `gchararray' passed as NULL 
May 12 11:36:22 pansen init: tty1 main process (3578) killed by TERM signal
May 12 11:36:32 pansen console-kit-daemon[3042]: WARNING: Unable to activate console: No such device or address 
May 12 11:37:05 pansen init: rc6 main process (8870) killed by TERM signal
May 12 11:37:49 pansen syslogd 1.5.0#5ubuntu3: restart.
May 12 11:37:49 pansen kernel: Inspecting /boot/System.map-2.6.28-12-generic
May 12 11:37:50 pansen kernel: Cannot find map file.
May 12 11:37:50 pansen kernel: Loaded 77794 symbols from 50 modules.