Try this in the shell console:
bt~# cd /etc/dhcpc
bt dhcpc # ls
dhcpcd-ath0.cache dhcpcd-ath0.info dhcpcd-ath0.info.old
bt dhcpc # rm *
the rm * (removes all your old configs), then try to connect wirlessly again.
Xploitz has also posted this
just put the hxxp:// before forums, I still can't post links.