Your mouse was not working properly b/c you the game did not have a hardware cursor for running the game in OpenGL and there was a patch someone made to fix it that you most likely had not ran. However, as of Tuesday patch 4.0.1 came out which was the pre Cataclysm patch and it added an OpenGL hardware cursor that you can enable in the options. This will resolve the issue with the mouse you were having. Also, addons work fine and you can even get the curse client running in WINE if you use that for your updates. Hope I was some help.
