Very often the best thing is to completely uninstall Flash and Java, then download and re-install them.
There can sometimes be problems uninstalling these, and you should go to the relevant websites for troubleshooting guidelines and the relevant uninstallers.
I recall doing this for Flash and Shockwave some years ago - seemed totally knackered until I did the comlpete removal, then all worked after reinstallation.
Other things to look at are browser security zone settings, browser plug-ins like No-script that prevent javscript running, or firewall settings blocking certain sites.
SD