LPent

I can't imagine it having anything to do with VMWare as a lot of people seem to be having this problem. Most of whom do not have VMWare and are not a member of a domain.
One other solution I came across was to disable IPv6, but that didn't work for me (maybe it will for you).
I have come to think that the solution to this problem is indeed not with IPv6 or uPNP even though it does seem to work for some (like me).
I have yet to see MS address this problem as I cannot find a reference to it anywhere on their KB.