In the interim, I sent the watch back to Aeris, and now I'm not quite sure what the problem was in March.
At that time, the battery had been replaced 6 mos earlier at Aeris, as a part of the 'hardware fix' to the battery drain problem that plagued Aeris and Oceanic for many years. They also did a nice job of sprucing up the exterior, in the process - it came back looking nearly new. I contacted them about the download issue and they had me try reinstalling the dive log software, to no avail. At that time, it wasn't downloading properly to either a new Win7 netbook, or the P4 XP_Pro machine that I had downloaded to for years. The repair guy said it might be the 'download chip'.
For the repair fee, I got what appears to be a new dive watch, with a year's warranty attendant to the repair fee. They didn't give me any diagnostic details about the old watch. This one downloads fine - the couple of times I've tried it - to the XP box, but the symptoms on the Win7 netbook are almost identical - the dive instances appear to download fine, with the aggregated data (duration, temp, max depth, etc.), but the profile details are missing for many, though not all, of the dives. I don't know what to make of that, and it's a disappointment not to be able to download to my travel PC, but I have a nice new watch that may promise to provide a few more years of core service.
I am slightly cynically awaiting the performance following the first battery replacement, which shouldn't come until after the warranty expires.