Hi there, the way around this is indeed to use Switch Converter from NCH. It is a cracking piece of software, and worth an investment. It can be obtained from http://www.nch.com.au/switch/plus.html

There is currently (Feb 2nd 2010) a slight bug with Switch, whereby the latest version of Flip4Mac (2.3) causes it to crash, and so it looks like it won't convert .wma files, although other file types are not affected. But, fret not, the solution to this is to use an older version of Flip4Mac. You can obtain Flip4Mac 2.2.3.7 at http://addictdownload.com/flip4mac-wmv-player-2-2-3-7/

Make sure you completely uninstall your existing Flip4Mac before replacing, using the uninstaller that comes with various versions of Flip4Mac - you may want to look for it in your applications\Flip4Mac folder, and run the uninstaller app there. This will not remove any license numbers you've paid for, merely the application itself. Then install Flip4Mac 2.2.3.7.

You will need both Switch and Flip to do the job, but they will, when properly put together, work in harmony to do lots of quick converting for you. And this should be quicker than working on iTunes in a windows environment - besides, why go there, isn't avoiding that the point of having a Mac?