Hibernation or sleep? You can try changing the way your computer sleeps in the bios, or try disabling sleep so there is no transition from sleep to hibernation. I have never had a whole lot of luck with desktops and sleep/hibernation and usually end up disabling it.
Desktop pc won't come out of hibernation. Tried power off/on but no help. Blue power light on, fan working but pc won't wake up. Running Vista.
I have a similar sounding issue with my HP tower running Vista. If it hibernates, the PC won't turn back on. The hardware power button won't illuminate for me when I press it, the fan turns on but the PC doesn't boot. The folks at Best Buy suggested that the power level from my outlet might have been too low. I've found that if I plug it into a different outlet then the hardware power button may work and lights up, but this doesn't always work. After getting a UPS to make sure I have clean power, I still have the problem. Will abandon hibernation and switched the default Power button in the Start menu to 'Shutdown' from 'Hibernate'. Seems like enough other folks have issues with hibernation on towers.