Meanwhile, here's another.  This crash seems like it may be correlated with suspend/resume somehow.  It never happens immediately after a suspend/resume, but as I recall it also never happens until at least one suspend/resume.

May 12 22:40:01 aethereal kernel: [22670.242629] ------------[ cut here ]------------
May 12 22:40:01 aethereal kernel: [22670.242635] kernel BUG at /var/lib/dkms/kvm/84/build/x86/mmu.c:640!
May 12 22:40:01 aethereal kernel: [22670.242637] invalid opcode: 0000 [#1] SMP
May 12 22:40:01 aethereal kernel: [22670.242640] last sysfs file: /sys/devices/pci0000:00/0000:00:1c.1/0000:0c:00.0/rfkill/rfkill0/state
May 12 22:40:01 aethereal kernel: [22670.242642] Dumping ftrace buffer:
May 12 22:40:01 aethereal kernel: [22670.242644]    (ftrace buffer empty)
May 12 22:40:01 aethereal kernel: [22670.242646] CPU 1
May 12 22:40:01 aethereal kernel: [22670.242648] Modules linked in: binfmt_misc i915 drm ppdev bridge stp bnep input_polldev kvm_intel kvm snd_hwdep sbp2 lp parport snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss arc4 snd_seq_midi ecb snd_rawmidi snd_seq_midi_event pata_pcmcia snd_seq iwlagn snd_timer iwlcore snd_seq_device led_class pcmcia snd mac80211 soundcore psmouse yenta_socket rsrc_nonstatic pcmcia_core dcdbas pcspkr iTCO_wdt iTCO_vendor_support snd_page_alloc cfg80211 serio_raw btusb joydev sha256_generic aes_x86_64 aes_generic cbc dm_crypt fbcon tileblit font bitblit softcursor squashfs unionfs nls_iso8859_1 nls_cp437 vfat fat usbhid usb_storage ohci1394 ieee1394 tg3 intel_agp video output
May 12 22:40:01 aethereal kernel: [22670.242687] Pid: 7022, comm: kvm Tainted: G        W  2.6.28-11-generic #42-Ubuntu
May 12 22:40:01 aethereal kernel: [22670.242689] RIP: 0010:[<ffffffffa03e2a30>]  [<ffffffffa03e2a30>] rmap_remove+0x170/0x230 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242702] RSP: 0018:ffff8800b6905988  EFLAGS: 00010246
May 12 22:40:01 aethereal kernel: [22670.242704] RAX: 0000000000000000 RBX: 0000000bcb8e7cff RCX: 0000000000000008
May 12 22:40:01 aethereal kernel: [22670.242705] RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffff88005910c320
May 12 22:40:01 aethereal kernel: [22670.242707] RBP: ffff8800b69059a8 R08: ffffc20014d86418 R09: ffff88005910c320
May 12 22:40:01 aethereal kernel: [22670.242709] R10: ffff8800b69059f8 R11: 0000000000000000 R12: ffff880119733000
May 12 22:40:01 aethereal kernel: [22670.242710] R13: ffff880001f35630 R14: ffff8800bd894000 R15: ffff8800b69059f8
May 12 22:40:01 aethereal kernel: [22670.242712] FS:  00007f6e52874950(0000) GS:ffff88011f803a80(0000) knlGS:0000000000000000
May 12 22:40:01 aethereal kernel: [22670.242714] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
May 12 22:40:01 aethereal kernel: [22670.242715] CR2: 000000006d000000 CR3: 00000000acd9d000 CR4: 00000000000026a0
May 12 22:40:01 aethereal kernel: [22670.242717] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
May 12 22:40:01 aethereal kernel: [22670.242718] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
May 12 22:40:01 aethereal kernel: [22670.242720] Process kvm (pid: 7022, threadinfo ffff8800b6904000, task ffff88005c0dacc0)
May 12 22:40:01 aethereal kernel: [22670.242722] Stack:
May 12 22:40:01 aethereal kernel: [22670.242723]  0000000000000000 ffff880001f35630 0000000000011583 ffff880048898000
May 12 22:40:01 aethereal kernel: [22670.242726]  ffff8800b6905a28 ffffffffa03e56f2 ffff8800b69059d8 ffffffffa03d7661
May 12 22:40:01 aethereal kernel: [22670.242729]  ffff8800acd9d7f0 0000000000000001 ffff8800b69059f8 ffffffffa03e286b
May 12 22:40:01 aethereal kernel: [22670.242733] Call Trace:
May 12 22:40:01 aethereal kernel: [22670.242735]  [<ffffffffa03e56f2>] paging64_sync_page+0xa2/0x1a0 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242743]  [<ffffffffa03d7661>] ? gfn_to_memslot+0x11/0x60 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242752]  [<ffffffffa03e286b>] ? gfn_to_rmap+0x1b/0x70 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242761]  [<ffffffffa03e4da5>] kvm_sync_page+0xb5/0x100 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242769]  [<ffffffffa03e4fe3>] kvm_mmu_get_page+0x173/0x460 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242777]  [<ffffffffa03e7890>] paging64_page_fault+0x280/0x510 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242785]  [<ffffffffa03e5bba>] kvm_mmu_page_fault+0x1a/0xb0 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242793]  [<ffffffffa040d297>] handle_exception+0x377/0x420 [kvm_intel]
May 12 22:40:01 aethereal kernel: [22670.242799]  [<ffffffffa040bc91>] kvm_handle_exit+0x121/0x2e0 [kvm_intel]
May 12 22:40:01 aethereal kernel: [22670.242803]  [<ffffffffa03e13ec>] kvm_arch_vcpu_ioctl_run+0x69c/0xbd0 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242811]  [<ffffffff80277ce9>] ? futex_wait+0x379/0x4b0
May 12 22:40:01 aethereal kernel: [22670.242817]  [<ffffffffa03d66a2>] kvm_vcpu_ioctl+0x2e2/0x5a0 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242825]  [<ffffffff8069e569>] ? _spin_lock+0x9/0x10
May 12 22:40:01 aethereal kernel: [22670.242828]  [<ffffffff80277718>] ? futex_wake+0xf8/0x130
May 12 22:40:01 aethereal kernel: [22670.242831]  [<ffffffff802f62d1>] vfs_ioctl+0x31/0xa0
May 12 22:40:01 aethereal kernel: [22670.242835]  [<ffffffff802f6685>] do_vfs_ioctl+0x75/0x230
May 12 22:40:01 aethereal kernel: [22670.242837]  [<ffffffff802f68d9>] sys_ioctl+0x99/0xa0
May 12 22:40:01 aethereal kernel: [22670.242840]  [<ffffffff8021253a>] system_call_fastpath+0x16/0x1b
May 12 22:40:01 aethereal kernel: [22670.242843] Code: 0f 1f 00 48 8b 57 18 48 85 d2 74 23 48 98 48 89 14 c7 48 c7 47 18 00 00 00 00 5b 41 5c 41 5d 41 5e c9 c3 0f 1f 84 00 00 00 00 00 <0f> 0b eb fe 83 f8 02 7f d8 48 89 fa b9 03 00 00 00 48 8b 72 10
May 12 22:40:01 aethereal kernel: [22670.242870] RIP  [<ffffffffa03e2a30>] rmap_remove+0x170/0x230 [kvm]
May 12 22:40:01 aethereal kernel: [22670.242878]  RSP <ffff8800b6905988>
May 12 22:40:01 aethereal kernel: [22670.242881] ---[ end trace 6671d0c9ca02de90 ]---