Thanks, Bob. While I have no trouble accepting responsibility, I highly doubt that it was anything I did. I was merely deleting tracks exactly the same way as I'd done many times before. However, since my incident I've read a number of other's tales of woe with "format disc error," which suggests to me a design flaw on Sony's part -- especially since Sony doesn't seem to have a clue about how to rectify this.
I forgot to mention that when plugging either my RH10 or RH1 (with the corrupted disc) into my computer, an "HMDHIFI" folder shows up onscreen with HMD files of various sizes inside. Would this help me at all?
Unfortunately, I never really considered editing AFTER uploading, since I assumed the RH10 was reliable both mechanically and electronically, and also because the operating instructions had an entire chapter on how to edit tracks on the recorder. Stupid me.
Regarding SonicStage, I'm running version 4.3. And yes, I did try uploading from an RH1, with no success.
So here we are...