Replying to What is this shit!?

[URL=http://s29.photobucket.com/user/BOUGHTON/media/ScreenShot2013-12-12at24719PM_zpsd2eb64ae.png.html][/URL]

Above is a screen shot of my latest film I exported out of FCP. The lower third is really "blocky"/"grainy". I am noticing this in some of my shots and I am wondering what the cause may be? I exported H.264 1280x720 24fps. The original footage is 1280x720 60fps and my FCP sequence settings match the footage identically. Anyone?