System Hangs but DVD/fan/kb light still working??

If my system hangs but my dvd drives can still open/close, my casing fans are still running and the keyboard will still light up when I press num lock etc, what is the issue?

To be exact, when my system hangs, ALL usb ports will have no power. Eg, my mouse will not have any light and my thumb drive will not have any light. But everything else including my PS2 keyboard, my casing fans, my dvdrw and my processor fans are all working.

does this means its the PSU problem?

I noticed that to be exact, when my system hanged, ALL usb ports have no power. Eg, my mouse has no light, my thumb drive has no light. But everything else including my PS2 keyboard, my casing fans, my dvdrw drive and my processor fans are all working.

I do not think its a PSU problem as this will either cause instant blackout/shutdown, not just hang. I was told it might be a USB problem with my mobo or maybe something to do with the casing.


I will probably try to run the bare setup outside my casing to see if it works

The PSU is an Enermax Liberty 500W. Been using this setup without any problems for the past 1 year.

Processor
AMD AM2 x2 6000+

Mainboard
MSI K9N Ultra

Graphics Card
Sapphire x1950 Pro 256MB

Memory
DDR2/667 Kingston CL5 3x1GB

Casing
CM Centurion 5

PSU
Enermax Liberty 500W

OS
Windows XP Service Pack 3