I don't know whether it makes any difference, but I have installed the esr (extended support release) version (you may choose at
http://mozilla.debian.net/ under "version)
Did you know, when you purge a package, the config files in your home were *not* removed! If you then reinstall this or a new package, you have the same config as before. So you always should make sure to remove or save away the config file/folders in your home if you want try a new install.
Maybe you could test the current install, but save away your home/IW folder.
You could try a live CD and install flash as a test, too.