Regardless of the web browser that you are using, you should be able right click on a Youtube video to bring up a menu then click on copy image url form the displayed menu. This opens box a box containing the image url. Then all you have to do is right click on the displayed image url and select copy. Then in your post click on the little film strip to open a dialog box, right on the text area and select copy from the menu then click on embed. That should embed the image url in your post in your post. I've never had any problem using different browsers. I'm running Windows 7 from a desktop and a laptop.