The fact that you can get some sound indicates that Flash Player is actually installed and partially working.
But you cannot get video, which still lets me suspect the graphic card drivers.
What I would do in your situation
- create a System Restore Point
- go to http://www.intel.com/p/en_US/support/detect and let it check for updated drivers
- go to http://www.nvidia.com/Download/Scan.aspx and let it check for updated drivers