If you happen to run Windows XP SP2 on a machine with more than a GB of RAM, you may likely see the following notification appear on the system tray:
This happens after hibernation is attempted. The error is: "Insufficient system resources exist to complete the API."
The solution is Q909095. There is a hotfix available, but you have to call Microsoft PSS to get it download the patch. It includes a new OS kernel which works flawlessly on my ThinkPad T60p with 2GB.
Knock knock.
[Update 10/17/2006, Download available]