If you go to the Bios and disable the onboard ethernet card....How fast and well does it boot then?
Are there no changes after trying that??
I was thinking if disabling the onboard ethernet and using a PCI Add on card would stop your problem....at least you could go from there.

http://www.tigerdirect.com/applicati....asp?CatId=587

I am not recommending TigerDirect or trashing them.Just a link for you to look at.