I'm having the same problem.
Highlight doesn't work accept my own nick.
What does work is:
* channel highlight in switch/treebar.
* Nick highlight in nicklist.
* Nick highlight in message and listbox of ONLY my own nick!!
What doens't work is OTHER USERS/NICKS highlight in message or nickname in channel.
I tried everything by reinstalling stuff removing extra scripts (not that many and no scripts that could cause this)
Cleaned up nick colors in address book and highlight , readded them but it doesn't seem to work else then my own nick.
