I notice you see this on resume from suspend:

Sep 25 00:13:20 quincunx kernel: [ 5942.889502] PM: resume devices took 5.468 seconds
Sep 25 00:13:20 quincunx kernel: [ 5942.889507] ------------[ cut here ]------------
Sep 25 00:13:20 quincunx kernel: [ 5942.889509] WARNING: at /build/buildd/linux-2.6.27/kernel/power/main.c:176 suspend_test_finish+0x75/0x80()
Sep 25 00:13:20 quincunx kernel: [ 5942.889510] Modules linked in: nls_iso8859_1 nls_cp437 vfat fat usb_storage libusual uvcvideo compat_ioctl32 videodev v4l1_compat af_packet binfmt_misc rfcomm l2cap bluetooth vboxdrv ppdev ipv6 acpi_cpufreq cpufreq_powersave cpufreq_conservative cpufreq_ondemand cpufreq_userspace cpufreq_stats freq_table container pci_slot sbs sbshc iptable_filter ip_tables x_tables parport_pc lp parport loop joydev arc4 ecb snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy pcmcia iTCO_wdt serio_raw iTCO_vendor_support snd_seq_oss psmouse yenta_socket rsrc_nonstatic snd_seq_midi pcmcia_core nvidia(P) snd_rawmidi i2c_core snd_seq_midi_event video output snd_seq snd_timer snd_seq_device snd soundcore wmi button battery ac shpchp pci_hotplug snd_page_alloc intel_agp dcdbas evdev ext3 jbd mbcache sha256_generic aes_x86_64 aes_generic cbc usbhid hid sg sd_mod crc_t10dif sr_mod cdrom pata_acpi ata_piix ata_generic libata scsi_mod ehci_hcd uhci_hcd usbcore dock dm_crypt crypto_blkcipher dm
Sep 25 00:13:20 quincunx kernel: mirror dm_log dm_snapshot dm_mod thermal processor fan fbcon tileblit font bitblit softcursor uvesafb cn fuse [last unloaded: cfg80211]
Sep 25 00:13:20 quincunx kernel: [ 5942.889557] Pid: 18348, comm: sleep.sh Tainted: P          2.6.27-4-generic #1
Sep 25 00:13:20 quincunx kernel: [ 5942.889558] 
Sep 25 00:13:20 quincunx kernel: [ 5942.889559] Call Trace:
Sep 25 00:13:20 quincunx kernel: [ 5942.889563]  [<ffffffff8024e8d4>] warn_on_slowpath+0x64/0x90
Sep 25 00:13:20 quincunx kernel: [ 5942.889568]  [<ffffffff80518dd6>] ? printk+0x6c/0x6e
Sep 25 00:13:20 quincunx kernel: [ 5942.889573]  [<ffffffff802126a4>] ? mcount_call+0x5/0x31
Sep 25 00:13:20 quincunx kernel: [ 5942.889575]  [<ffffffff8027de35>] suspend_test_finish+0x75/0x80
Sep 25 00:13:20 quincunx kernel: [ 5942.889578]  [<ffffffff8027df44>] suspend_devices_and_enter+0x104/0x1b0
Sep 25 00:13:20 quincunx kernel: [ 5942.889580]  [<ffffffff8027e201>] enter_state+0xe1/0x110
Sep 25 00:13:20 quincunx kernel: [ 5942.889583]  [<ffffffff8027e2ea>] state_store+0xba/0x100
Sep 25 00:13:20 quincunx kernel: [ 5942.889587]  [<ffffffff803a55e7>] kobj_attr_store+0x17/0x20
Sep 25 00:13:20 quincunx kernel: [ 5942.889590]  [<ffffffff8034ae0a>] sysfs_write_file+0xca/0x140
Sep 25 00:13:20 quincunx kernel: [ 5942.889593]  [<ffffffff802eb81b>] vfs_write+0xcb/0x130
Sep 25 00:13:20 quincunx kernel: [ 5942.889596]  [<ffffffff802eb975>] sys_write+0x55/0x90
Sep 25 00:13:20 quincunx kernel: [ 5942.889599]  [<ffffffff8021288a>] system_call_fastpath+0x16/0x1b
Sep 25 00:13:20 quincunx kernel: [ 5942.889600] 
Sep 25 00:13:20 quincunx kernel: [ 5942.889601] ---[ end trace 2b44916d971937bc ]---
Sep 25 00:13:20 quincunx kernel: [ 5942.889728] PM: Finishing wakeup.

I'm not sure whether this would be responsible for a crash though, and there isn't any evidence of the crash after this point. Looking at the kernel source for that warning, there is the following comment:

	/* Warning on suspend means the RTC alarm period needs to be
	 * larger -- the system was sooo slooowwww to suspend that the
	 * alarm (should have) fired before the system went to sleep!
	 *
	 * Warning on either suspend or resume also means the system
	 * has some performance issues.  The stack dump of a WARN_ON
	 * is more likely to get the right attention than a printk...
	 */