Same problem here, i hope this info helps.
The nvidia driver prevents me from hibernating, switching to nv solves the problem.
(but the nv driver doesn't work well with the two 1920x1200 screens)

I also think this is related or similar to ubuntu bugs 94332 and 68258.


root@laika:/etc/acpi# hibernate --force
Some modules failed to unload: nvidia
root@laika:/etc/acpi# lspci
00:00.0 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:00.1 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:00.2 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:00.3 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:00.4 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:00.5 PIC: VIA Technologies, Inc. K8T890 I/O APIC Interrupt Controller
00:00.7 Host bridge: VIA Technologies, Inc. K8T890 Host Bridge
00:01.0 PCI bridge: VIA Technologies, Inc. VT8237 PCI bridge [K8T800/K8T890 South]
00:02.0 PCI bridge: VIA Technologies, Inc. K8T890 PCI to PCI Bridge Controller
00:03.0 PCI bridge: VIA Technologies, Inc. K8T890 PCI to PCI Bridge Controller
00:03.2 PCI bridge: VIA Technologies, Inc. K8T890 PCI to PCI Bridge Controller
00:05.0 CardBus bridge: ENE Technology Inc CB1410 Cardbus Controller (rev 01)
00:06.0 FireWire (IEEE 1394): Texas Instruments TSB43AB22/A IEEE-1394a-2000 Controller (PHY/Link)
00:08.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8169 Gigabit Ethernet (rev 10)
00:09.0 Multimedia controller: Philips Semiconductors SAA7133/SAA7135 Video Broadcast Decoder (rev f0)
00:0a.0 Network controller: RaLink RT2500 802.11g Cardbus/mini-PCI (rev 01)
00:0f.0 RAID bus controller: VIA Technologies, Inc. VIA VT6420 SATA RAID Controller (rev 80)
00:0f.1 IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)
00:10.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
00:10.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
00:10.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
00:10.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 81)
00:10.4 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 86)
00:11.0 ISA bridge: VIA Technologies, Inc. VT8237 ISA bridge [KT600/K8T800/K8T890 South]
00:11.5 Multimedia audio controller: VIA Technologies, Inc. VT8233/A/8235/8237 AC97 Audio Controller (rev 60)
00:11.6 Communication controller: VIA Technologies, Inc. AC'97 Modem Controller (rev 80)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
02:00.0 VGA compatible controller: nVidia Corporation GE Force Go 7800 GTX (rev a1)
root@laika:/etc/acpi# uname -a
Linux laika 2.6.20-16-generic #2 SMP Thu Jun 7 20:19:32 UTC 2007 i686 GNU/Linux
root@laika:/etc/acpi# dpkg -l nvidia\* | grep ii
ii  nvidia-glx-new           1.0.9755+2.6.20.5-16.29 NVIDIA binary XFree86 4.x/X.Org 'new' driver
ii  nvidia-kernel-common     20051028+1ubuntu7       NVIDIA binary kernel module common files
root@laika:/etc/acpi#