TwistedBard

Interesting. I don't think it could be IRQ's, so I wouldn't exert too much energy in that direction. Set those back to auto and let them work themselves out.

Other things you could look at would be perhaps the motherboard shorting out on something (an extra motherboard stand underneath or a stray piece of case contacting a side of the board), or the video card may not be seated completely in its slot (pull it all the way out and put it back in). That last one seems very likely to me.

Hope you get it working!