This is what I have just done:
Unistalled mIRC
Cleaned up the registry and one or two files the uninstall left behind.
Re-Installed mIRC 6.12 from a fresh download.
Ran mIRC and connected to a server.
No other changes made to config
then waited untill about 5 of the nicks turned red
Closed mIRC
Re-Done the same thing as above but this time I removed everything in aliases.ini, popups.ini and urls.ini before I started mIRC.
And its still the same
ie whenever a user joins or types a message - the name on the right nick list turns red which i'm not able to change.
Now I'm going to try a fresh install of windows on a new hard disk to see if that helps....