Yes, it sounds like the very same problem. True, it is extremely hard to identify the noise, perhaps it is resonating through the engine, but I put my ear right up to the oil pan (almost on it) when it was running and it did seem to come from right there. But who really can be sure?
And yet the car keeps running fine. The AC works perfectly. I just drove it 100 miles today with the AC on, including stop and go rush hour big city downtown traffic. No problem. Like you, I am also very, very concerned about it stranding my wife and kids somewhere in the unknowable future.
Other thoughts I've had:
--motor mount--I jacked up the engine slightly, to take what I thought would be weight off the mounting. No change.
--removed and replaced the serpentine and tensioner, no change
--felt the power steering pump, seemed ok, no change
--tightened the center bolt on the crank pulley, it was already pretty tight, no change
-went to the Toyota dealer to look at an '06 Sienna!