PC Shuts Down Completely During Sleep

About a year ago I build a home brew dektop PC. I am running Windows 7 Professional, I7 processor, Asus P6T Deluxe Ver. 2 motherboard, 6gb ram.

Occasionally, in the past when the the PC would sleep it would not wake up when I pressed the keyboard and had to be restarted instead. Over the last week the problem has occured more frequently. Today it happened every time the PC went to sleep and was not woken up within a few minutes. I have never made any adjustments to my power setting in Windows or the BIOS. I am using a balanced power scheme.

I get the following error message from Windows upon reboot:

Windows has recovered from an undexpected shutdown.

Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.1.7600.2.0.0.256.48
Locale ID: 1033

Additional information about the problem:
BCCode: 9f
BCP1: 0000000000000003
BCP2: FFFFFA800637AA20
BCP3: FFFFF80004535518
BCP4: FFFFFA800927A7C0
OS Version: 6_1_7600
Service Pack: 0_0
Product: 256_1

Files that help describe the problem:
C:\Windows\Minidump\012111-32604-01.dmp
C:\Users\Howard\AppData\Local\Temp\WER-56019-0.sysdata.xml


Is this a Windows 7 issue? Is it a hardware issue? Any ideas how I can correct this error?

Hi Howard08560,

STOP 0x0000009F: DRIVER_POWER_STATE_FAILURE
Usual causes: Device driver

Please see:

Windows 7 - Blue Screen of Death (BSOD) Posting Instructions.

Attached are the files referenced in BSOD reply. Please let me know if this helps isolate the problem. Thanks.