I have two different WIN 7 computers here doing exactly the same thing. They go into sleep mode and frequently don't come out. Occasionally on my machine the OS has a message that says that the Video Driver had become unresponsive but it was successfully restarted, then it asks if I want to see if there is any answer for my trouble at MS central. I have never heard anything back from that.
My computer is built on an ASUS P5B deluxe with the bios recently updated. My wife's is build on an Intel motherboard and they both have the E8400 processor and they are not over clocked. Memory in one is 3Gbytes and 6Gbytes in the other. The common thing is that we both have NVIDIA 8500GT graphics cards. I have the most recent NVIDIA drivers which are dated November of this year - 195.62. The OS is Windows 7 64 bit and both machines were set up with a fresh install.
When I change the power settings for constant run the systems are stable. It's the sleep mode that is killing them. I rather would like to have the sleep mode working.
The MiniDump Analysis of 9 crashes of my machine are all the same:
On Sun 1/3/2010 2:35:36 AM your computer crashed
This was likely caused by the following module: ntoskrnl.exe
Bugcheck code: 0x9F (0x3, 0xFFFFFA8005F34060, 0xFFFFF80000B9C518, 0xFFFFFA8005DE3E10)
Dump file: C:\Windows\Minidump\010210-22417-01.dmp
file path: C:\Windows\system32\ntoskrnl.exe
product: Microsoft® Windows® Operating System
company: Microsoft Corporation
description: NT Kernel & System
The crash took place in a standard Microsoft module. Your system configuration may be incorrect, possibly the culprit may be another driver on your system which cannot be identified at this time.