Your answer seems a contradiction. Your mIRC is recognizing and not-recognizing the /notice command at the same time.
If I did
//asdfg $me test
There would be nothing in the way of a "->" message on screen, so the fact that you're getting that arrow message tells me that your mirc knows that /notice is a communications command. But on the other hand, you're visually seeing the message in status window that NOTICE is an unknown command.
The only way I can see both being true is if you have something that intercepts the ON NOTICE command and mutes it so you can't see the notice being received by you. I suspect that if you have another person willing to test with you, that if you did /notice that-nick message, that they would see it.
For NOTICE to be at the same time an unknown command - one way this could happen is if you have an alias trying to send a notice, except it has an alt-160 touching the /notice, so it looks like NOTICE is an unknown command, but what's really unknown is NOTICE $+ $chr(160)
As for your trouble with /w or /whisper, these are not mirc commands, they have to be an alias you created, and without letting us know what it is, we can't help with it.
