I would uninstall then reinstall FF

http://support.mozilla.com/en-US/search?q=flash+player

Sounds like your security settings are set too high and not really allowing installing of apps like flash.

Maybe this will work.

1. Close all programs
 2. Open your browser
 3. On the tool bar, select TOOLS
 4. Then select INTERNET OPTIONS
 5. Then click the SECURITY TAB
 6. Then set your security to the LOWEST
 7. Click APPLY
 8. Click OK and close the browser
 9. Reopen the browser and go to a sight that has flash and it will ask you
 for permission to use the player
 10. Say YES