[blimey]

First, provide link to the video, or an example video.

Next, the flash web player at many viacom sites will cough up the 720p link only if the player is in full screen mode at the time the flash web player initiates the connection.

Lastly, many viacom site videos (even 720p) are much more easily accessed using http links that have been uncovered from cell phone OS and tablet OS reverse engineering.