Works fine here. You have to make sure your IAL is updated. Type /help IAL to learn how $address gets the host information-- in short, if the user was on the channel before you joined, mIRC will not be able to return anything for $address() until you /who # (or another command that gets the host of the users on the channel). This has ALWAYS been how mIRC has worked, nothing has changed in this respect.
In other words, when Wims said you were lucky, he meant that, previously, you've been using your script only on nicks that joined the channel after you did, and therefore the IAL was filled with their host information.