Shoutbox

I had the nastiest case with this ever.  It may not be exactly the same as yours, but this started happening on my work laptop, at one of our offices only.  The error seemed to come back very quickly, as if it didn't even try to connect.  It wasn't only happening sometimes, it wouldn't work at all.

I went through testing with another account, uninstalling and reinstalling Messenger several times, once trying to manually clear out anything it might have left behind in the registry, flushng DNS cache on both the laptop and the actual DNS server on the network, looking for changes in firewall policies, having the laptop's private IP address translate to a different public address in case mine was "banned", everything.  Nothing worked.

What puzzled me was that it would work when I was anywhere else, including our other offices -- which are sharing the same exact internet connection over the WAN.  The only difference between the office A and the office B was the local IP address ranges.

I couldn't see why, but since nothing else had worked, I changed my private IP address reservation anyway, and was shocked to find that fixed the problem.  Furthermore, I could put the laptop back on the old private address and it wouldn't connect again.  I can probably still do that and replicate the problem.  It's the equivalent of changing a computer behind your home router from 192.168.1.2 to 192.168.1.3.  It shouldn't make any difference, right?

I would love to hear a guess from one of Microsoft's developers as to what may have been responsible.  There is NO functional difference between the old IP address that makes Messenger not work and any others which work fine; no different firewall rules, nothing.  I am the network administrator and I know this.  Oh well.