If you are receiving the error message, “Your CD key is disabled from ladder play.” when trying to join or create a ladder game, this indicates the CD-Key that is installed has been temporarily or permanently banned from playing ladder games on Battle.net. Even though the CD-Key is restricted from playing ladder games, you are still able to play Custom games with other players on Battle.net.
Warcraft III CD-Keys are regularly banned and accounts are closed due to hacking on Battle.net. In the case of the CD-Keys that were banned, at least one account tied to each CD-Key was identified as having used such a program while playing on Battle.net. First offenders are banned from ladder play for one month and repeat offenders are banned from ladder play permanently. Users who are unsure if their CD-Key was temporarily or permanently banned will have to wait one month from the time the CD-Key was banned to determine the status.