When I first boot my Windows 7 computer, it will go idle if I stop using it - first the screensaver comes on, then the computer goes to sleep after a certain amount of time. This is the expected behavior.

However, after I've used the computer for awhile without rebooting (after about a day or so), I've noticed that it stops going idle - the screensaver won't come on, and the computer won't sleep, no matter how long it sits unused.

I've confirmed that the idle timer is increasing as expected via GetLastInputInfo. However, it looks like something is interfering with the results from CallNtPowerInformation. Every 14 or 16 seconds, the TimeRemaining value jumps back up to its maximum value when I query SystemPowerInformation.

I've used the SysInternals Process Monitor to detect any unusual events that might be happening to trigger this reset, but come up empty. Does anyone know exactly what are the possible causes of TimeRemaining resetting to its maximum value?

I'm fairly sure that it's not my mouse, keyboard, or network sending spurious events, because I've disabled each one and the problem continues to occur. This would also reset the GetLastInputInfo timer, which is not happening. I'm looking for something that affects SystemPowerInformation TimeRemaining, but does not affect GetLastInputInfo.

Thanks.