It is my understanding that multicast does not play well with WiFi. Google that, I've never tried.
mms: or mmsh: might be the key, although WMP doesn't support it anymore, so version dependant (maybe)
.ja.
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http://forums.techarena.in/media-server/648624-2.htm
VLC Multicast 224.0.0.1:7777 works just fine with WIFI, i used to use it all the time to muticast MPeg2 DVDs over the LAN through my old and slow 22Mbit/s (MAX bitrate,more like 15Mbit)11g kit (3COM) and VLC/MPC/MP9 with the right codecs/splitters decoding it (ffmpeg is fine)on the PC playback devices etc.
it might be that some 11g routers dont pass on the multicast packets due to some oddball firmware setting, so you might need to search on yours....but it does work fine for many people.... and switchs should'nt care as they dont process any packets, just passes on whatever comes along.