WHo the heck who uses OSX would want to view wmv files hahaha Ok, so QT can't play them & wmp always gives errors. So try out either VLC: http://www.videolan.org/vlc/ (choose nearest mirror site) or see its abilities here: http://www.videolan.org/vlc/features.html

Or try MPlayer http://mplayerosx.sourceforge.net/ which is about the same (personal preference!)