Odd problem after rendering.
 

It's kinda of hard to explain but after I render my movie, when I view it certain parts of the movie are messed up by black or white squares.

It shows up randomly and sometimes it's just a little and other times its like the whole screen : / I don't know what it is or how to fix it, any help would be appreciated.

Here's a pic

http://img460.imageshack.us/my.php?image=squareswk6.png
http://img235.imageshack.us/my.php?i...quares2nq5.png

This is probably the worst it gets, then switches back to normal at random..