the manual seems to indicate all 4 PCI slots should operate at 8x. it could be that the 32-bit OS can't handle all that bandwidth. you may want to try asking ASUS as well.... good luck.
Hmmm... interesting. I'll probably check out the OS first and see if it's because of that. I might actually just try installing Ubuntu on it instead and test if the problem still exists.
Looks like it's the OS + software that's causing the issue according to this thread
http://forum.bitcoin.org/index.php?topic=19038.0I guess I really have to use Ubuntu to get all 4 going.