Thanks to all who replied. I thought I had it solved yesterday, after re-installing the rim tape more carefully, as the tire held air for my entire ride yesterday afternoon. However, this morning, my tire was flat again, and it definitely has a slow leak. How slow? Well, I've re-inflated it here at work to a full 97 PSI and it has no apparent leakage. It's been 3-4 hours, and the tire remains fully inflated (as determined by the gauge on my pump). I'm guessing that a tire wire or similar tiny sharp is my likely culprit, and I'll need to spend some real time at home finding it, using the methods described. Of course, the one issue that seems to speak against this is that the holes have been more toward the 'rim' side of the tube... not right against the holes, but definitely well inside the bead of the tire, I think...

Rim tape: Cloth rim tape is what is installed, but whoever at my LBS installed it did a crap job, as it was really crooked and not covering the entire circumference of all of the holes. Having said that, it does not appear that it is the cause, as I repositioned it very carefully, and further, the holes I found in the tubes were tiny pin holes, and there was no 'stretch' or 'strain' on the rubber of the tube around the offended area. I'm not ruling it out, but it seems less likely?

Pinched tube: While that might have been true of one of my attempts, I was pretty careful in the subsequent attempts. Also, that usually shows, in the form of some kind of irregularity on the rubber where it stretched or tore. These are tiny pin-holes in the tube with no apparent scuffing or straining of the rubber.

I'll update when I finally solve this! Thanks again to all.