Look for basic connectivity issues. If you're seeing the AP, but not getting DHCP leases -- what does an "ifconfig -a" (aka /sbin/ifconfig) return? Assuming you're getting a IP -- do you get a default route (netstat -rn), or proper entries for DNS? (cat /tmp/resolv.conf.wlan0).

Most problems I've had have been DNS related -- but indications are that your system isn't connecting to the AP properly. Make sure you've selected the proper authentication type (that is; none), and that all the right icons are indicating unlocked, etc.