One laptop connects, other fails everytime using WRT54G/WPC55AG

Hoping someone can help me work out where I went wrong in my configuration.

I have the following configuration:

o: Linksys Wireless-G Broadband router: WRT54G connected using PPPoE w/ DSL
modem
o: Desktop into router with CAT5 - no problems
o: P4 XP Pro Laptop a/b/g internal connecting to WRT54G - no problems
o: PIII Win2000 w/ Linksys PCMCIA card: WPC55AG - fails to connect with
"cannot associate with access point" in the WLAN "moniter".

Linksys router is set for:

DHCP - 50 clients
WEP off
MAC address access w/ each MAC in the list
Same SSID throughout

If I turn off MAC address access on the router the WPC55AG can connect after
a lengthy time and I see the MAC address in the status/DHCP client list. If
I use this same MAC address in the access list and turn it back on it fails
to connect.

Also, WPC55AG with the MAC filter off takes a very long time flashing
between "scanning/connecting..." in the WLAN monitor before it settles for
my router even though it's the only one is the list and the default
connection. The link/signal strength is ~6/8 when it connects so I don't
believe it's a signal problem.

I installed the Win2000 drivers as instructed so I'm at a loss but it's been
bugging me for a week now and I can't work it out; yes, it's 2am central
time and I'm still trying to get this right.

Are there any better monitor programs than the Linksys WLAN monitor to help
pinpoint the problem?
Any ideas on a configuration to make the WPC55AG connect consistently and
quickly? or connect at all really?

Any and all help appreciated.
Regards,
PK