I've downloaded the new version but, after the installation procedure it doesn't work.
I've modified the preferences in safari but still not working.
I've norton antivirus in MAC but it doesn't work as firewall.
I know the last updates in MAC OS have changed security protocols but I'm not able to see any video where flashplayer is needed.
First off... GET RID of that garbage from Norton!!!
1. You DON'T need anti-virus for Mac because (and I want to be absolutely clear about this) THERE IS NO SUCH THING AS A VIRUS FOR OS X. (See: https://discussions.apple.com/message/23885605#23885605)
2. Of all the so-called anti-virus products for Mac, Norton has got to be the worst, without a doubt.
3. Even if you run Windows in BootCamp or as a Virtual Machine... You ONLY need anti-virus on the Windows partition or in the VM. ANYTHING that can infect a BootCamp partition or VM CANNOT affect your Mac OS X partition... at all.
4. Anti-virus products for Mac CAUSE more problems than they could ever possibly resolve. OS X is more than capable of protecting itself from "malware".
Stepping off my soap box, Try a "clean install": How to perform a "clean install" of Flash Player in Mac OS X
99.9% of the time, that will resolve your Flash Player issues.