I have a laptop which runs on Windows 7 Ultimate. I normally run a dozen of apps while working, such as Visual Studio 2010, Outlook 2010, Eclipse, VMware Player, Chrome and various RDP session. I usually reboot only once a week, so I put it to sleep when I'm on the move. Sometime when I put the laptop to sleep, it hang after a few seconds (Basically the HDD led blink for a few second, then stops, but power led not blinking, indicating it's not sleeping yet). Try to wake up the laptop will not work, and the laptop remain in that state forever, while it will continue to heat up if I put it into the bag.
The laptop usually is able to sleep for the first time after a fresh reboot. I wanted to find the cause so I can solve it as hibernating is too slow for me.
EDIT: It's similar to this w520 sleep freeze