It's possible the Hibernation file may be corrupt, and needs to be deleted and re-created. Open your Control Panel and select Power Options | Hibernate | Uncheck the box next to "Enable Hibernation", and click "Apply". Next, perform a Disk Cleanup...Start | All Programs | Accessories | System Tools | Disk Cleanup. Afterward, reboot your computer (this will delete your existing hibernation file) | Go back and enable Hibernation, reboot twice more (you need to reboot twice because XP needs to take a consistent snapshot of your system profile)...and you'll have a new Hibernation File.