Flash plugin is not detected by firefox

[jeremy-list]

This is a re-occurrence of bug #41442. Flash was actually working for me on raring ringtail until I ran apt-get upgrade this morning. Now ubuntu software center and apt are claiming that flashplugin-installer is installed, firefox is claiming it's not.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: flashplugin-installer 11.2.202.310ubuntu0.13.04.1
ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
Uname: Linux 3.8.0-19-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Fri Sep 13 16:38:17 2013
InstallationDate: Installed on 2013-08-19 (24 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
SourcePackage: flashplugin-nonfree
UpgradeStatus: No upgrade log present (probably fresh install)