I posted this as response to another wireless issue as well:
I've noticed that linksys will sometimes take a hex key and lower case
the key. When you put it in your system, my Dlink for example wont take
lower case. It assumes its all uppercase. My SGB modem though takes it
either way and keeps it how I put it in. Depending on what the coffee
shop has equipment wise, you might try all uppercase and all lowercase
in the key and see if that helps.