I was having a horrible time with the flash the other week, and now have a little digital sticky reminding me that when I uninstall the flash plugin in preparation for a clean reinstall, I need to also first delete the following files (Mac):

\Library\Internet Plug-Ins\Flash Player.plugin\

Library\Internet Plug-Ins\flashplayer.xpt

~\Library\Preferences\Macromedia\Flash Player\

~\Library\Caches\Adobe\Flash Player\

Hope a reboot and/or clean reinstall of the plugin helps you too!