To the best of my knowledge the sleep bug issue occurs due to the fact that this mobo is extremely picky when it comes to PSU-s.
Many people on several forums have instantly fixed their sleep issues with this mobo by using another PSU.

This apprears to effect mostly higher end modular PSU-s. Especially from Corsair HX series.
Unfortunately for me i have Corsair HX1000 but my friend has SeaSonic S12II 520W PSU and hes PC has no problems waking from sleep mode.
Also reported problematic are AX-850 and HX850.

I dont have another PSU laying around to test this tho but i've looked into this problem quite thoroughly so im pretty sure this is it.
http://hardforum.com/showthread.php?t=1579942 <-- Page 8 or 9 is where the PSU issue is discovered.