All of the above.Explain your problem more.
Are you right-clicking a unit, and trying to rename it?
Are you trying to change the proper names?
The Editor Suffix name?
Nope i didn't use any of the above.That sounds like just a general WE problem.
Are you using NewGen or WEU or something?
If so, delete, re-download, and reinstall them.
If not, try reinstalling WC3.
It doesn't take that long