in recent_viewed_xml.php

Look for

video_duration

change to

video_length

That should fix it.

You can also change the amount of "recently viewed" from 5 to another number. As it is right now, the same 5 keep rolling until someone watches something. You do that where it says LIMIT 0, 5"; you can change it to LIMIT 12"; (or some other number) which is what the roller for version 2.6 was set for.