I had an issue very similar to this one - http://www.sevenforums.com/network-i...able-conn.html
(old thread, please don't post to it)
I also posted to the MS Windows 7 Beta board at Connect and was contacted by an MS engineer to run some trace apps they have.
I have been unable to reproduce that horrible litte hiccup since ten so I haven't been able to help them with those traces yet, I'll see if they maybe want to talk with you about this. If they reply back I may PM you for your email addy so I can forward it to them.