Not sure but sometimes I couldn't change it also. I think it is a server problem. Because at a time I changed my nickname on my laptop, stay sometime and then sign out. At the evening I signed in in my desktop and after about one hour my new nickname came there. Also sometime I can't change it like you.
You might want to check if the following is enabled:
Tools > Options > General.. "Use the same display picture and personal message wherever i sign in"
You could try if turning off (unchecking) the option i mentioned..then signing out and back in again and enable it again makes a difference..
If the computer you are using at home isn't a shared one you can make sure Tools > Options > Security .. "This is a shared computer..." isn't ticked. Even tho that doesn't mention your nick...but hey, could be worth a try
This post was edited on 04-20-2007 at 03:04 PM by Sunshine.