Very odd. Before I read the whole post I suspected the spider gasket came completely loose and jammed things up. With the top off, which houses the handle, spring, and movable valve part, does it turn freely? If not then something is wrong with the top part. There is an O-ring seal in that assembly and you can take it completely apart. Never had to do it to mine though but it looks pretty easy. Best I can do for now.
Al