Thanks for your comments and advice, Poconos and duraleigh.

I added about 4 lbs of Borax in increments over the past two days without any movement in pH. (I wonder if this was because the Borax had been sitting open in my laundry room for the past seven years.) Switched to pH Up (sodium carbonate, HTH brand) from Wal-Mart and about one pound has me back up to pH of 7.5

With a little more CYA, chlorine is now doing great as well. TA is right at 100, so I'm good to go. I use Ben's kit, of course.

BTW, the posted pool chemistry calculator requires PC Windows to run, unlike the Excel file last year for simple chlorine calculations. For us Macintosh users, nothing comparable that I can find.