In Chrome 34.0.1847.116 on Mac OS X 10.9.2, this configuration (specifically the lack of
type="video/mp4" on the
source element) of video.js causes the
notSupportedMessage error message to be dislayed by the video.js player. Although I can see the error message has been added to the DOM, it's not visible and it causes the
vjs-poster element to be pushed down the page, resulting in one copy of the poster image overlaying the other.
I've raised this as issue 1164 in the video.js repo.