I have near to the same problem...only mine is a recurring one. I fixed it
about a month ago by uninstalling a program that Dell Installs by default
that interferes with Outlook. BUT now it is back. no program or anything.
I also noticed that my network is getting flooded with bloody tcp requests
that microsoft vista is sending about.

I am in dire need of this fixed as it is one of my project co-ordinators
laptops. Thanks,
Erik