My personal desktop, running 32-bit Windows XP SP2 (with 4GB RAM, 2.75GB addressable, swap disabled, hiberfil.sys existing and contiguous on C:\; SP3 is not installed because SP2 has been working fine and I do not want to re-qualify with SP3 just for sheer perversity) typically gets hibernated at night. For a long time this worked great, but recently the machine has had trouble entering hibernation.

Sometimes when I press my power button (configured to hibernate), the box will start the procedure for hibernating (i.e., go to the blue "Windows XP" background logo and display a message about entering hibernation), but before displaying the usual blue-on-black hibernation progress bar it will drop back to the desktop. No error messages appear, on screen or in the system log. The only record of unsuccessful hibernation attempts in the system log, which proudly proclaims that "The Windows Image Acquisition (WIA) service entered the running state." once per failed hibernation attempt.

The problem is almost certainly resource related: if I then close one or more applications which are running, and repeat the exact same process, the machine will hibernate perfectly. There does not appear to be a reliable high-water mark for virtual or physical memory use, below which the machine is guaranteed to hibernate; it's different every time (though typically, below about 1.1–1.4 GB memory usage seems to be where hibernate succeeds most often). Memory may not even be the relevant resource; as far as I know, it could also be handles or sockets.

This behavior is relatively recent: it has only started in the last few months; before then, I could hibernate reliably no matter what the current resource use of the system. This machine claims to have hotfix Q909095 installed, but since the symptoms of my problem match KB909095 rather well, I'm suspicious if this fix is actually working as intended.

Any ideas on how to fix this or where to start debugging?