Problem booting GX280 with network boot disk

I'm having an issue with the GX280. We have MS client boot cd which connects us to the domain, maps a drive to our image location. The problem is on some of the systems, the network login stops at "Initializing TCP/IP via DHCP" and does not progress any further. I've tried the Broadcom diag disk, resetting the bios etc.. to no avail. The only way I get past this is to boot the system with a drive which is already imaged and after that, I can boot from my cd with no problems. There appears to be some setting on the nic which won't allow the connection to be made but I can't find it so far. The Broadcom diag disk has not been much help. Any clues as to what our problem is will be much appreciated.:mansad: