Very weird problem

I posted this in the graphics section first, because I thought it was just my GPU fan that was doing this, but tonight i realized its actually every fan in my computer. Now it seems to me like its more of a motherboard issue.

Basically for the last 3 nights, AFTER shutting down my system, every single fan seems to go up to 100% and stay that way. Tonight I waited 5 minutes and they still kept going. What makes this even weirder is that it seems to always happens around the same time(when i turn off my PC around 1am). I ve done numerous shutdown cycles in the last few days and its only happened 3 times...at around 1am every time.

While the monitor/keyboard/mouse all are non-responsive, the light on my power button pulsates. It only does that when the computer is in "sleep" mode, but like I said, pressing the keyboard would not "wake up" the computer. So this leads me to believe it was not quite 100% shut down.

Also, if it makes a difference, before the first time this occured I had forgotten to disable my onboard graphics in the BIOS. I finally disabled it yesterday(I also enabled "plug n play" ), and a few hours later this happened...so maybe they are somehow linked. I did disable plug and play today but the problem did happen again.


The problem itself is nothing more than a minor headache, but is this maybe a symptom of a bigger issue down the line? Any help greatly appreciated!

Here is my system:

Gateway DX4200-09
Windows vista home premium 64 bit
BFG 550W power supply (quad 12v rails, 20A on each)
Foxconn RS780 motherboard
1.8Ghz Phenom x4
2X2GB of DDR2 667/800 MHz SDRAM
Serial ATA 640GB HD
Radeon hd3200 integrated graphics(disabled)
Radeon HD4770

Thanks!