LAN Freezes on Start-up

[Ouiji]

I am building a system with a EPOX 8K9A2+ mobo that has an integrated LAN card. I have installed Win XP. When I boot the machine with the LAN connected to an active WAN/DSL modem, it hangs up the network connection for about 1-2 minutes after Windows loads and is ready to run. All the other features in Windows will work, but all network features are unaccessible. If I try to restart, Windows will not let me until the LAN unfreezes. If I boot the machine without an active modem connection it works fine.
I have installed every possible driver for the LAN and relaoded Win XP twice. I have even installed a seperate PCI LAN card (disable intergral LAN) and still have same problem. I have been using this same DSL modem with Win XP on another machine without problems.
Thanks for any suggestions.

[sleddog]

I'd start by carefully comparing all network settings and network-related services between the problem machine and the working machine. It seems the problem machine is trying to do something on the network that is failing and it only becomes responsive after some task or tasks time out. An obvious one is maybe DHCP. Is that service started?

[Ouiji]

Good idea, but I have alrady gone thru all the LAN settings in Win XP. Even went so far as to try Win 98SE on a spare HDD and got the same result. Win98SE requires a third-party client for my ISP/set-up. At this point, I have tried every possible software setting and even a different NIC, so it has to be something with the motherboard. I have used the modem and cables with other systems for a long time without troubles, and still do. Thanks for the ideas.