Video too big in preview & nothing appears after adding the video

When I add a video and preview it, the video is too wide, how can I change the size of the video that is show? You can see what I mean in the screenshot below.

Also, once I click to add the video, nothing happens. It doesn't show anything new, not even the text I added to the staus box.

Photos also have the same problem, both uploaded and linked, and also adding links.

However, just adding a post update does work.