Windows Live Messenger 2011 was not signing in

Recently I upgraded to the latest Windows Live Essentials 2011 with Live Messenger in it. I found out that from a corporate network I couldn’t get it to login. When running the troubleshooting option I saw it stopped at “Key Ports”. I first suspected the proxy server, so I went onto another proxy (yeah, at one customer I have multiple exit points), but that did not work either. From home it did work (I run an ISA 2006 there).
By chance I got it to work again today, because I needed to move back to the previous proxy server on that corporate network due to some other thing. What I did was set the proxy settings in internet explorer to Automatically detect, and after that set it back to the proxy settings I needed. That step seemed to do the trick and simply moving back and forth between proxy servers did not.
A colleague of mine pointed me to a thread on the ISA forums and after scrolling to the second page I saw a link to this page where Lawrence Cawood found this exact same solution/workaround.
Well perhaps it is some bug somewhere. Happy I got it to work again.
If you run into it.. give it a try and good luck!
Bob Cornelissen