Try to reconnect those files. Go to File > Reconnect Missing Files. As you know the location already, just browse to that location.
See if it solves the problem.
Thanks, but the problem is not that the files are missing (I tried your suggestion, and the program tells me that the files are already there). The problem is that instead of showing the picture in the organizer, it shows the grey screen with the hour-glass. When one clicks on it, the picture appears. But once one tried to work on five or six pictures in a row, then it becomes a guessing game re: which photo is hiding behind the grey screen.
If you are on Windows platform, goto the location : %programdata%\/Adobe/Elements Organizer/Catalogs and double click the folder whose name is same as your catalog. On MAC the location you go to would be : ~/library\Application Support\Adobe\Elements Organizer\Catalogs
Now there must be a file with name thumbs.cache. Simply rename it.
Launch Organizer and see if thumbnailing happens now for your catalog. If not, run the following two commands-
File >> Manage Catalogs >> Select your catalog >> Optimize
File >> Manage Catalogs >> Select your catalog >> Repair
Went through the suggested steps. It will not repair. Tells me I have
a corrupted catalog, and suggests going to a backup. My problem is that
I have (or cannot find) a backup. Does this mean I have to remove the
program, re install it, and start all over again?
Did you try catalog repair and optimize?
You don't need to reinstall. First try catalog repair and optimize and if that doesn't work, you may create a new catalog for test sake. To do so, click File > Catalogs > New.