When I started up my computer and started Firefox 7.0.1 this morning, all my personal settings were gone. All the add-ons were still there, but my settings (both Firefox settings and add-on settings) were gone. It looked as if Firefox and all the add-ons had been newly installed. I didn't install any (add-on) updates in the last couple of days, nor any other updates (such as Windows updates). Fortunately, I had backups of all my settings, so the problem was easily solved, but I'd like to know how this happened.