I was getting similar "Application packages missing" error messages whenever I tried to install anything.

Bruce Forsberg's answer turned out to be the solution, but he didn't give enough detail for me to fix it.

1. In the Application Manager, I had to open the menu and tap on "Tools", then "Application catalog...".
   • This brought up the list of software sources.
2. I tapped on "Maemo Extras", then on the "Edit" button.
   • Note that there were two entries for this "Maemo Extras" and "maemo Extras" (note the lowercase 'm')
3. Changed the value of the distribution field from "freemantle" to "diablo"

I've never intentionally modified these software catalogs, but I install and uninstall software regularly. So, I guess something added the "freemantle" automatically.

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