Had a lot of things on my to-do list, but a few were left undone since i discovered the kitchen sink was leaking. Loosened the lock nut, raised up the drain, rolled up a replacement bit of plumbers putty, and replaced that which had deteriorated. Tightened it all up and voila! it seems to be working now. However, i did notice the flat rubber (located between the lock nut and the bottom of the sink) is stretched out of shape – had better get a replacement on hand just in case.