Check around the site here, I think you'll find there are several issues with the drivers. Have you recently had any updated Intel drivers loaded?
I have several Dual Intel 82573L based systems that have dumped, and now no longer have MACs, only way to get working is to Enter the MAC manually?
I have currently disabled the onboards, installed (thank gosh I have 2 (only) slots free on these 2Us. arrgh) thank gosh #2 that I had a local generic PC shop nearby sell me 20$ Idaknow DLink or TelNets or somethings, prob have Realtek or Broadcom chips, thank gosh #3, that got my client up and running.
$120 worth of low end NICs solved my problem, Let hope INTEL can solve the driver issues