Stumped as a Brazilian Rain Forest : Onboard Networking goes dead after installing Radeon 9100

Help! I can't figure this out. Any ideas appreciated.

My onboard LAN suddenly stopped working (Gigabyte 667 Ultra2 mb). No
Internet, no Local Area Network. Nothing.

Only precipitating event - I just popped in a new video card (Sapphire
Radeon 9100 AGP; latest drivers on Win XP Pro Service Pack 1). That's
it. Nothing else was changed.

Now, when I look at the network cable plugged into the back of the PC,
the two indicator lights on the Lan port are green steady/yellow
flashing. And *no* LAN related functions work. XP's Hardware Device
Manager says all drivers are enabled & functioning.

Is this a wake issue? Perhaps the new video card tricked the onboard
lan (82540EM Intel chip) into permanent sleep? If so, how do I wake
this thing back-up?

Many thanks,

J Greenman
Detroit

P.S. I'm using a SURFBoard cable modem connection (Comcast), plus a
Linksys SR41 router - & my other PCs work fine. I plugged the problem
PC into a working PC's network cable. Still no go. Tried plugging
into other router ports (that work on the other PCs) - no go. Tried
restarting both router/cable modem - working PCs still work, troubled
PC doesn't.

In summary, NOTHING has changed other than the video card/Radeon
driver install. What could this be? Like the title says, I'm majorly
stumped. Any ideas? I need to hear 'em.