Hmm, I just fixed the sink in the second bathroom. Somehow. It was draining excruciatingly slowly, and I was fiddling with it to see what was required to either plunge it or get the drain plug out so I could pour some nasty chemical down it, and something about my manipulating the drain plug suddenly made it drain much more rapidly. I did a lot more pumping of the plug, open-close-open-close, and now it's just like new.
I wish I had a better mental image of what was going on down there. But I shouldn't look a gift horse in the mouth. Kathy (the roommate come fall) should be pleased since that will be her bathroom.