Reinstall Flash, and if you are using an Intel-based Mac, make sure you are installing the correct Intel-compatible version for the Mac.
The best way to reinstall Flash is to run the Adobe's Flash uninstaller first, then run the Flash installer. Then repair permissions with Disk Utility because Adobe's installer fouls up Flash's permissions settings. (Not to a the degree where Flash won't run, it will, but you will see plenty of permission corrections pertaining to Flash when you repair permissions.)