hmm.. pretty much everything seems to check out compared to what <normally> fixes it or fingers a networking issue getting in the way.
Anyone done a malwarebyte scan (or other similar tool) that found something to remove? Anything suspicious showing up in any one's add/remove programs list?
This may have to be shifted to the bug reports or support portal if no one else has any ideas... hate to shuffle it over there, but our best chance of getting SE to look at it closer.