Recently I upgraded my system to LGA2011 CPU and used Gigabyte GA-X79-UD3 F20 motherboard. I used to have problem with sleep mode in Windows 7 Ultimate 64bit and I tried everything with no luck at all.
All the sudden, I think my PCI sound card (Audigy ZS2) may cause the sleep problem?!? Yep, I took it out and the sleep mode is now working like it should.
If anyone has the same problem like me, you can try to take some add-on cards out 🙂
Remember, before you do anything, check the Gigabyte’s website for latest BIOS update.