As more security is imposed you see this happen. For video files I prefer VLC PLAYER since it side steps the decoder issues.
For youtube you want to try their HTML 5 options.
Macbook pro - 13in running os 10.6.8.
I have a video problem that just appeared out of the blue. I can't display some video images and some pictures.
Specifically if I try to watch a you tube video I get a blank screen - but I can hear sound. If I control click on the video and select "popout" then then video will play normally.
Using MplayerX 2 I can no longer watch any videos on my computer.
Using Preview I can not seen any of the pictures on my computer but I can see the thumbnails. If I use Nikon View photo software I can see the pictures just fine.
Obviously this is not a hardware problem. Some setting somewhere has gotten messed up but I can't find it. HELP!