hi datadrop ~
at your suggestion i re-installed picasa 2 and ran it and lo and behold it showed all my photo file directories.
i then deleted some photos in picasa, then restored them from the trash bin, then closed picasa and re-opened it, thinking picasa would re-scan my photos and i'd be able to see the briefly-deleted ones again.
picasa was unable even to find the directory they're in...
...i give up
~ beau