Interrupts process maxing out CPU with 3650 installed?

I have an ASUS small form factor system I use in my AV setup. It's an old system, just an Athlon 3000, but I've got a 3650 which lets it handle HD video perfectly fine. But recently it's been absolutely terrible, and I finally figured out why.

I used process explorer, and found that the interrupts process is constantly using 50 to 60% of the CPU at all times. If I take the 3650 out and go back to integrated video, the interrupts go away. I've reinstalled drivers to 10.4, but I'm thinking it's not really a driver issue since it happens in XP, 7, and 7 safe mode. (Haven't tried XP safe mode but I doubt that would help)

Is this the sign of a dying motherboard or videocard? I don't have any other cards to test in the system, none of them will fit nor is the powersupply powerful enough.

Hm, I installed the card in my desktop and it booted up -- but never showed anything on my monitors. I was able to VNC in, but absolutely nothing on the monitors. I guess this card is just dead.