Just thought I would contribute with a problem and my resolution.
Put together a new build with P8P67, 2500k, Windows 7 32bit, Sapphire 5770, Dell monitor ST2410 with HDMI. Ran Asus auto tune software to bump up my clock speed to 4.3.
My problem was resuming my computer from sleep, specifically my monitor. The computer would go to sleep, I would press enter/esc/move mouse and hear the computer wake up but the monitor would stay in sleep mode.
Tried unplugging HDMI, turning monitor off/on etc. and still couldn't get the monitor to display. Had to turn off the computer and back on.
Through the several iterations of rebotting trying to figure out the problem, there were in some (not all I think) where I got an Asus message saying had to re-overclock again (sorry, don't remember the exact message) which I did.
Had an epiphany yesterday and decided to let the computer/monitor go into sleep without the overclock. It went into sleep and I was able to resume the computer/monitor with enter/esc.
My conclusion is the Asus overclocking caused the problem.
I have had the same problem - mouse, keyboard and monitor don't respond (don't even seem to get power?) after my OC'd computer wakes up. I discovered that the culprit is the CPU PLL voltage setting. If this is turned on in either the BIOS or using the ASUS software, then the computer does not come back properly after going to sleep. If the PLL voltage is turned off, the computer wakes normally.
The only problem with this is that I can't get much of an overclock with PLL voltage turned off, so that kind of defeats the purpose of having a system that you can overclock. If I run stock (which of course is not too shabby!) then everything works fine.
My current solution is to physically shut down the computer every time I walk away from it. When I power it back up, it works fine. My other solution - never letting the computer power itself off - was too wasteful of energy so I ruled that one out.
I haven't figured out if this is an a) ASUS BIOS issue, b) an ASUS motherboard hardware issue, c) an Intel chipset issue or d) a Microsoft Windows issuse. I'd love to hear from ASUS on the issue.