After installation of the original WoW followed by the Burning Crusades, I launched the application. The 'Launcher' window displayed correctly, so I pressed the 'Play' button.
A few screen refreshes later, I was looking at the license acceptance screen. Although I was able to move the mouse pointer around, it seemed as though none of my mouse clicks were being recognized. This prevented me from being able to 'Accept' the license agreement.
I then use the NVidia Settings application and disabled 'Xinerama' (I have a dual monitor configuration with an NVidia 7600 GT controller) support. In the /etc/X11/xorg.conf file, this looks like this:
Section "ServerFlags"
Option "Xinerama" "0"
EndSectionAfter restarting the X11 server, everything works fine.