All these new P5k series boards seem to have some messed up USB hub issues that can hang the bios at bootup. Took me forever to narrow it down.

So if you're still getting problems with hanging bootups just realize it's lousy USB hub support and try shuffling what's on the hub or just disconnecting it completely. A lame workaround but apparently the only other solution is to roll back to 0504, except that'll give some unknown CPU errors since it doesn't fully support most of the newer CPUs.