I'm using mine with the wireless card and the airport. The only trick is that you have to go to the Airport Utility->Base Station Menu->Equivalent Network Password to get the wep password for it.
As to how to piggy back off the computer's connect, I just don't know.
for the equivalent password (hex value) do you have to put a $ sign in front or just the literal value in the CLIE WEP field. I tried both with and without the $ but no go... ;(
I set up the SSID of my network to exactly my base station name. i.e. capitals matter.
Under WEP, I chose 40/64 bit: 10figures(Hex)
I'm pretty sure the key is the number without the $ sign. (I'm not at home, so I can't test it)
Under Connect mode, I'm using Infrastructure
If you have these set up, you might check your Airport settings:
Under Airport:check to make sure 'Enable encryption' is checked
Under Network: Distribute IP addresses is on
Under Access Control: if you have access control on, you will need to add your clie. (Don't know how to do this one, but I assume its possible)
Linear Mode
