Powerbook Ti / Time Capsule connection failure

I have a Powerbook G4 Ti 1ghz running Leopard and am unable to connect to my time capsule. I enter the correct password and then get a 'failure' message. The connection works fine via ethernet.
Any ideas?

Welcome to the Forum. Has it ever connected or is this an initial set up of TC? The standard Airport on that unit was 802.11b - is the TC Network set to for 802.11b?

It has never connected but I do have two other machines working well, those being a white macbook and an ibook g4
I have not looked at the settings on the TC but will do that.