Sorry, I don't what is going on, Since I don't have the TubeAce Wordpress theme. I am sure somebody else here can help you though. Maybe there is an option that can be changed on the import with the plugin you are using. Here is what I noticed.
I notice the Broken Teens video works fine and it is an MP4 video.
Monstrous black cock doesn't faze this teen slut | Twatta Tube
look at the source
Code:
<div class="flowplayer" id="player" data-swf="http://twattatube.com/wp-content/plugins/tubeace/libs/flowplayer/flowplayer.swf">
<video preload="auto" src="http://mh.promo.brokenteens.org/media/2236605/564e1f1c1a3b1.mp4"></video>
Here is the Hustler Video, That isn't playing. Notice the mp4 extension is not attached.
My First Lesbian Experience 3 | Twatta Tube
Code:
<div class="flowplayer" id="player" data-swf="http://twattatube.com/wp-content/plugins/tubeace/libs/flowplayer/flowplayer.swf">
<video preload="auto" src="http://secure.assmeat.com/gallery/MzAwMTY1My4yLjc0LjIxNC4xLjEyNTA1NS4wLjAuMA"></video>