I've seen this problem posted many times on the net while I was searching for an answer to the same thing. I saw many different things to try to correct the problem but no joy. Well last night I called Linksys tech support to try and figure out the problem. After going through one tech for an hour he referred me to a second level tech. Here is what he had me do...
Took the card out of child's room to my computer by the router and installed it. Set up a new Network using "WEP" and 64 bit (not 128) encryption with a 10 digit key. The card worked fine, connected and could browse the net. I was using WPA2 PSK or Personal with a 24 digit key in my child's room before. I took the card out and back to my child's room and set everything up as WPA2 PSK with only a 9 digit key and it worked like a charm. The tech mentioned that sometimes a long key can get lost in the translation between the two and shorter is probably better. I checked on length of a safe passkey for WPA and found that 8 or 9 digits is good, especially if you use upper and lower case in the key.
I don't know if it was putting the card in the other machine and it cleared something out or it was the shorter passkey but it does work now!