If i return to my windows 7 x64 computer after it has been idle for a couple of minutes it will respond for 3 seconds and after that everything freezes for around 5-30 seconds and then the computer starts working normally again. The freezing time varies and some times it even get stuck there forever requiring a hard reboot.

This is very annoying as you can imagine, it's almost as slow as resuming from hibernation every time you left it idle enough to turn off the monitor.