When I click on a link to go to a youtube video, the video pops up for a few seconds in the correct location of the website but then a square ad appears on the left side which forces the video screen to be pushed all the way to the right and off the screen. The video then appears to the right side of the column of "popular viewed" videos. A scroll bar will sometimes appear at the bottom of the window because the page is now a lot wider, which will allow me to scroll completely to the right in order to see the video, however, sometimes the scroll bar does not appear and I can only see the very left edge of the video.

I reinstalled Adobe Flash Player which didn't help and I also have the most recent version of Firefox. This started happening fairly recently....maybe a week ago or so.