there is nothing in native mirc that will stop nick change command from working. Do you have any scripts loaded? If so they might be causing the problem. If not, then as an admin you should be able to see debug information and see what the system is seeing and how it is handling the nick change. I still feel this must be a script or ircd issue, not one with mIRC.
Do you have any scripts loaded? > no not this time i left them out, not only does this happen on their server I am on, it also happends to other servers 3 in fact. Like I said if i uninstall mirc and reinstall it work fine for a bit and then quit working. This is what I am stumpped on this issue. I was thinking is it due to my name Brother_Jim, I can change my name if I go to connet and manually change it their like i am goingto log in with that name. Each time I try to change my name, I get the message to change your name back type /nick newname message, it like it is saying my name has been changed but it does not. Strange.