I have a 2009 MMS and Printopia works just fine. It found my wireless HP printer and scanner and works like a charm. Just installed it and enabled the settings under System Preferences.
bigbearf
I just tried to use Printopia here on my network (running G5 10.5 Server) but I ran into an issue where my wireless network and wired network are on different subnets and bonjour doesn't play nicely over subnets.
I have also had issues with different wireless routers that don't allow bonjour to have communication between wired devices and wireless devices, even on the same subnet.
Either of these two problems could be ailing you, at least worth checking out.