Can't get wireless card to connect to router

Hi. I've got a 2wire SBC DSL modem/wireless router in my study, and a
windows 98 SE desktop across the house. I can't get my new wireless card
(linksys WMP54G) in the desktop to connect to the router.

Now here's the weird part: I have a laptop with a linksys WPC54G card, and
it connects to the router just fine, so it's not a problem with the router,
and I have another router in my room (Linksys WRT54G), which my desktop (the
one with the new Linksys WMP54G) connects to effortlessly, so it's not a
problem with the wireless card.

Whenever I go to the WMP54G's Wireless Network Monitor and press "connect"
on the linksys router's SSID it immediately confirms that I'm connected, but
when I go to the 2wire's SSID and enter the WEP key (which I'm positive I
have right) and press "connect," it just sits there forever and refuses to
connect.

I've been all over the net and nowhere does there seem to be an answer to my
question. How is it possible for a computer to connect to one router, but
not to the other???