Jezzarino, I would need to try to replicate this behavior, we haven’t heard anything about this.
Are you running the latest BIOS version and drivers?
Which processor are you using?
Latest BIOS, latest drivers, latest XTU, happens under Windows 7 64bit, Windows 8 64bit and Windows 8.1 64 RTM
CPU is a 3930K
Set the machine to sleep after x amount of minutes. Machine sleeps. Wake it up, then wait again for it to go to sleep, and it will fail...