Thanks for the replies. I resolved the problem, although in a highly unorthodox way.
Autosketch wouldn't install, complaining about the missing fonts. I could have skipped them, but that would have resulted in reduced flexibility within Autosketch.
Examining my Windows\Fonts folder revealed that several font files were listed as zero-length, and several others had slightly incorrect names. I copied the folder's contents to another folder. By doing so, the "special treatment" of the font files was eliminated in the second folder. All of the copied font files looked normal and properly named. I then deleted all of the fonts that I could form the original font folder, then copied them back from the second folder. Everything is normal now.
Hopefully, this is an isolated issue. I'd not like to think that something else nasty is lurking in the wings.
- John