What make and version of browser and version of windows are you using? Are you logged in with admin permissions? Have you tried another browser (download Google Chrome or Apple Safari and try it there)
Also check it isnt disable in your add ons.
Don't rule out the problem beig with the clips and not your browser. If you saw the flash logo after installing, it is installed fine. There are millions of knackered clips out there, trust me!
Any doubt, try and uninstall flash and reinstall cleanly.