For your Mac: When it requests your password type in the "Encryption Key." I found this information under "My Network Settings" which I was able to access through a PC. (I'm sorry, I don't know how to get that info via my Mac but I never even tried since I had originally set up my Linksys with the PC.)
I read many forums searching for the answer. I tried the "$" sign in front of my password with no luck. I changed to WPA security and no luck... I found the key and That Was IT!
Best of luck to you!