cupajoe,
It is a real shame they didn't make an AMV Convert Tool for a Mac.
Try this site:
http://www.macwindows.com/emulator.html
It lists some PC emulating software you can install on a Mac. Hopefully after that, you can install the AMV Convert Tool.
In the meantime, if you have some .WMV files which are fairly small (ie: less 30 MB's) and they are good to share, you can upload them on the site and I can convert them for you and put them on the site for everyone else as well
.