Sorry to double post but after manually repairing most of the thumbnails as I mentioned above, I found a few more and attempted to "Search for and repair missing thumbs" via the admin panel again...............and it worked! lol
I looks like I got past whatever image was causing the problem when I did the manual repairs as it completed the process all the way to the "finished" message this time and actual repaired the ones I found.
I'm still curious about deleting files that are not needed anymore. hehe