Why sound but no video?

I have tried using the steps on the flash player help forum. When I'm trying to watch a movie trailer I get sound and no video. I have tried right clicking on the playback and going to settings. When I click on settings I do not get the display box. This also happens on the box for flash player help website. I have deleted player browser data and removed cache. What else can I try to do to correct the video issue. I have also checked for updates on my drivers and all are up to date.