Make sure that your router has WEP enabled, and key type is set to Automatic. Either 64 or 128 bits is ok. Ensure that the only key 1 (if multiple keys are optional) is enable, and that it all characters in the key are hexadecimal values (ie 0 to 9 and/or A to F.) Some router models have been found to have difficulties, such as the NetGear WGT624 v3.