To follow up with myself here (until V@no or Jan or someone with more brains than me does), I just wanted to update that I double checked with the hosting company - the path to the convert utility of ImageMagik is still correct.
AND I tried uploading throught the Admin Control Panel and using the "auto-thumbnailer" feature there. Although it *said* the thumbnail was created, it was not shown on the Category page. Instead, a full-sized image was. :/
Terry