That's not technically a bug, per se. Windows considers certain names to be devices and so mIRC does as well. Granted, that's pretty much an outdated method of determining devices, but I don't believe Windows has chosen to drop it even in Vista.
In any case, you're looking at a very small number of names that cannot be used and there's absolutely no reason why you *have* to use them, so just change to something else instead.
