Try changing the security in the router (WEP [which would mean that the phone is a very insecure phone], AES, TKIP). If that works, keep the new security, and reconnect all your other devices. (They'll still keep trying the old security setting.) If it doesn't work, just set the security in the router back to what it was, and accept that, probably, the "security" in the phone is a bit abnormal.