Problem solved. There was an update to ZoneAlarm Security Suite, that caused the blocking. The solutions provided by a ZA support tech, was to do a clean install. Had to uninstall, then run a Clean uninstall utility program provided by them, and then download the latest version all over again.
And, that did the trick.
Through all the hassle, one good thing came of it, the Universal Media Server recommended by DreMarceaux. It's just like PS3 Media Server, only it doesn't choke on streaming MKVs. Thanks for the suggestion.
Dazed and confused over high tech.
Sigh...Concrap. The Internet Overlord Cometh
They're not com-tastic!