Ethernet "seizures" on MacBook Pro (coincide with IGMP membership reports)

Question

In a nutshell, nearly every time my Mac blurps out a seemingly normal IGMP Membership Report (V1 & V2), it goes mute for anywhere from a couple of seconds to tens of seconds before returning to normal. Of course, a span of that many seconds will cause an iChat Video stream to crash and burn (as well as stall downloads, delay web page loading, etc).
During this "mute" period, the Mac quits talking to any other hosts and does not appear to hear any unicast traffic while continuing to hear (as evidenced by my packet captures) normal broadcast traffic.
I've written a more detailed description of this problem on my blog where I can provide a diagram showing the packet captures that illustrate what I'm describing:
http://www.halfpress.com/archives/2006/11/frustrating_os.html
I wouldn't normally link a post here to an outside site, but the diagram and other details are important to my description of the problem.
What I can summarize here, though, is that the problem appears to affect only my ethernet interface (not when I use AirPort) and seemed to start happening for no apparent reason earlier this week. The closest correlation with a software update or other installation was iTunes 7.0.2 some hours before first witnessing the start of the issue. I'm not saying that caused it... but it's a factor worth considering.

Answer 1

I'd look to the router you might be using.
I was getting these same blips with a Linux-based PC running as a firewall ('smoothwall') and would drop the iChat connection audio/video/both, with precisely the same message. NoDataReceived. ([edit]changed routers, video worked again).
See if you can eliminate the router as the cause?
We can see from reading about IGMP, is that it's a "hey, are ya there?" protocol used between routers and hosts.
There are security issues.
This might be a firmware issue with your router.
Get the mac out from behind the router onto the modem itself for these tests... and see if you can videophone to mom...
Otherwise, I can't see why this is a Mac issue. (your blog is nice, though Nice pic on the arc d'triomphe. We did that OUR first jet-laggy morning in Paris, too...don't look down.