Try to run wc3 as Administrator.
Edit: If it doesn't work like this, here is something I found by an official Blizzard poster:
Quote
If you're running Windows Vista or Windows 7, you may want to install Warcraft III in a non-protected folder. Try installing the game in C:\Games\Warcraft III and see what happens.
This post was edited by Nerubian on Jun 30 2011 01:57pm