Delete (or better, rename/backup) the file extensions.rdf. Firefox will recreate it when it is next started.
This solved the problem for me. No need to create a new profile. -- "installLocation has no properties" error in nsExtensionManager.js during install/update of extensions https://launchpad.net/bugs/65609 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
