I have discovered that the problem is definitely in the Gnome config files in the users home directory. If I delete that stuff (.gnome, .gconf, etc.) at least then all I have to do is log in as the user and restore the custom desktop settings (like the size of the panel, single click to open, etc., etc.). That's a lot better than having to restore ALL the desktop launchers, as well as ALL the application settings (like Pan, Evolution, Firefox, ...). I am trying to home in on exactly which single file needs to be deleted (because it's corrupted).
I also have a suspicion that this has something to do with selecting the "save current settings" option on the logoff screen. The craziness seems to occur if I check that selection while a Samba share (on a Windows machine) is mounted to the Linux machine. If I unmount the share and THEN log out and save settings, it doesn't seem to happen.