Long story short, sometimes an app becomes corrupt, and those of us "in the know" know that simply reinstalling the app will often fix it.
Now that the updater is part of the platform, it seems that it would be trivial to offer a "Repair" feature. Right click the app, choose Repair, and it uses the updater to reinstall the app (either through a cheap hack: set the version a point lower in appinfo.ini and launch updater, or by sending a switch/argument to the updater to update just that one app).
Also, there are a couple files in the Profile folder in Firefox that can cause issues; perhaps if the latter option were done above, an argument/switch could be passed to the Firefox installer (which would also have to be updated, of course) to make it delete the files in question, I think it's the .json files, but I could be wrong.