Oh....that's strange. Why is your image width not 100% then?
Have no idea. Another MS magical stuff, I believe? Hehe It doesn't really surprise me because MS is a company not afraid of showing you the blue screen of death even during a new product launch presentation! LOL
EDIT : I just editted the image size from the HTML source editor. This seems to work, too : <p><img width="450" src="DIRECT LINK OF IMAGE" /></p>