Strange Behaviour with Multicast.

[Rob White]

I have two fairly simple applications, one is a management app that
multicasts requests for status to a number of clients, most of the time
the clients happily receive the multicast and respond in kind with
another multicast back to the management app. This works fine for a
whole bunch of time (anything from 2 mins up to several days), then for
no good reason the management app stops receiving the responses sent by
some, but not all of the clients. The clients are definitely still
responding, but the data is not getting back to the management app.

I've been trying to track down what's going on for a couple of
weeks now and it's getting really frustrating.
I'm running on fully compliant IGMP switches, my management app is
running on server 2003 with a GB connection and the clients are XP
Embedded with 100MB connections.
My suspicion is starting to point at the switches behaving strangely,
but that's difficult to prove. Has anyone seen this type of behaviour
in .net apps?
Oh and the management app sets it socket up like this, maybe I've set
something strange:
IPEndPoint localEP = new IPEndPoint(bindAddress,
m_appSettings.ManagementMulticastPort);

m_multicastSocket.Bind(localEP);

MulticastOption mcastOption = new
MulticastOption(m_appSettings.MulticastAddress, localEP.Address);

m_multicastSocket.SetSocketOption(SocketOptionLeve l.IP,
SocketOptionName.AddMembership, mcastOption);

m_multicastSocket.SetSocketOption(SocketOptionLeve l.IP,
SocketOptionName.MulticastTimeToLive, 1);

I'd be really gratefull for any help.
Rob