Dying motherboard? (Asus A8N-SLi)

[shaithis]

I have been trying to figure out whats going south in my rig....

Crashes started a few days ago, completly out of the blue. System just freezes, no Blue Screen, no errors in eventlog and I never get a message on restart saying what crashed it...
That is in Windows x64.

I have changed the PSU and have also swapped RAM and RAM slots to elliminate them as the problem. I have also checked the chipset fan which seems to be running fine.

I then installed normal 32bit Windows XP on a spare partition.....Windows XP will not load the drivers for:

OHCI Compliant IEEE 1394 Host Controller
Texas Intruments OHCI Complient IEEE 1394 Host Controller
Standard Enhanced PCI to USB Host Controller
Standard OpenHCD USB Host Controller

They all show with yellow ! next to them......I even had to plug a PS2 keyboard in to get through setup and to navigate the desktop. I tried deleting the above devices from device manager and rebooting....they re-detect again but still fail to load the drivers.....then installed the Forceware 6.66, still the same, unintalled FW 6.66..same...etc etc

Boot back into X64 and all the devices are working fine but you get random lockups when trying to do anything intensive. Boot back into normal XP and no USB or firewire.

Could XP and XP64 show different symptoms for a dying motherboard? or can anyone think of another explaination for whats happening?

I am currently leaning towards RMAing the board back to Scan but don't want to incur a re-stock fee if it isn't it.

[shaithis]

Just noticed that the BIOS isn't assigning an IRQ to the USB controller.....

Can't say I have noticed wether it has in the past.....nor can I find a BIOS option to enable it.

Can anyone with an A8N confirm that theres shows an IRQ for the USB controller on the POST screen?