Decided to call AppleCare again, wondering if my "inconsistencies" issue AND a widespread warning to input my password when moving anything to the DT (a permissions problem NOT solvable in the "traditional" manner) were somehow related. These are the only recurring problems of my MtnLion install.
BINGO!
It took about an hour on the phone with another "Senior" but it's now TOTALLY copasetic. Did all kinds of steps (few of which I would come close to accomplishing w/o him sharing my screen) starting with Terminal, then going to Recover Disk, and other nether regions, including several "visits" to Mac OX Utilities. He had me remove the plist, only once. Many of the other elements of the "treatment" we did multiple times.
He said they have been getting more than a few calls about permissions and MtnLion recently, so he was clearly not unfamiliar with the circumstances.
I would find it impossible to recount all the highways and byways of the OS visited this morning. But it's all solved, now, thank goodness . . . and Tim Cook.