General :: VLC RTP Streaming In FC12?

I'm trying to get VLC to work streaming RTP audio/video over my office network. The goal is multicast a/v streaming. In all test cases, we are streaming from VLC to VLC. I am able to stream from Windows to Windows, and from Fedora to Windows, but not from Windows to Fedora. Additionally, I am unable to receive a LOCAL stream from one instance of VLC to another, within Fedora.

I don't see any reason why this would be. The buffer indicator (where the elapsed/total time is normally displayed) never shows any connectivity, so it would appear to be a network problem, but since I am able to stream from Fedora to Windows (same IP, same port) I thought it would be something else.Does anyone know of a solution to this issue?

EDIT: Correction to previous edit: the IGMPv3 protocol was just not being picked up by Wireshark. Reverting to IGMPv2, I am able to pick up the Membership Report, Join, and Leave group packets from the Linux machine. I'm using the GUI to configure the following:

CLIENT
rtp://@239.255.12.42 :rtp-caching=1000
SERVER:
screen:// :screen-fps=30.000000 :screen-caching=300 :sout=#transcode
{vcodec=mp4v,vb=800,fps=30,acodec=mp4a,ab=128,channels=2,samplerate=44100}
:rtp{dst=239.255.12.42,port=5004,mux=ts}
:no-sout-rtp-sap :no-sout-standard-sap :sout-keep

MOST of this is default settings, for the given methods, which I haven't really changed. I've also tried adding the :5004 to the client URL to explicitly give the port, but received no different effect.