Both my computers would not wake after sleep once windows 8 was installed.
I updated both chipset drivers from the amd site. NOT from the motherboard page but from the general "amd chipsets" for windows 8 page. Both computers seem to be working now. (note: neither of my motherboards have windows 8 drivers listed on the motherboard pages yet)
I think its the AHCI drivers specificaly, but not sure.
hope it works for you.