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)