Hi all -- OP again --

Thanks for the tips. Regarding the water hose pressure jet...When I
removed the trap I was amazed at the amount of water that continued to
flow in from the tailpipe and into the bucket.

Normally, when I take off a trap, I get a few dribbles but 99 percent
of the water that I get I get from emptying the trap. In this case,
with the amount of water that came back, I figure several ounces
already must be part way up the stack....We're not talking gallons or
anything, but probably a good pint or so came back...

I think I will try the vent first, just because it sounds easy and
won't hurt anything and then move on to more drastic measures....

Thanks again.