Just a quick note - I just ran around and around with a sap54G wireless access point and a A+G card with a problem that was very deceptive. I wasn't able to connect with either the windows software or the linksys software - no error messages, no warnings, no log information. After turning off and on just about everything that I could find I found out how to fix it! I had to remove all of the entries in the MAC address filter - EVEN THOUGH I WASN'T USING MAC ADDRESS FILTERING! It must be a bug (I even tried updating to the lastest firmware) with Linksys - but just to let you know, if you are having trouble connecting to a wireless AP, look at the mac address filter table and make sure that there are no entries in there.
Good Luck! M