|You don't say if this happens with all video, or just online ones. Does it happen in just one player, or all players you've tried?|
Do you have on-board video, or is it a dedicated card? If on-board, do you have enough memory allocated to graphics/video in the BIOS settings?
Check your graphics cards properties/settings for an "overlays" setting. Play with this setting to see if it makes a difference.
You might even try downloading the latest driver for your graphics card. Never use updated graphics drivers from Windows Update. They are often worse than the original driver they have replaced. This may even be your problem. Try rolling back the graphics card drivers (easiest from within Device Manager).
I'm getting old and my memory isn't what it once was, so I'll have to post back if I can think of any other possible fixes.
Please let us know if you found someone's advice to be helpful.