First of all Update all the drivers.
If issue still exists then restore the registry settings.. Read this thread.
http://social.technet.microsoft.com...-7-ultimate-x64-registry?forum=w7itprogeneral
If issue is not resolved then:
Changed the Power Management settings in the BIOS to:
Hope issue is fixed.
- Disable power on from PCI devices
- Disable power on from LAN