Hi guys, this is my first post as I’ve just joined.
I’ve also been having the same problem and discovered that VC Reflect from Video Copilot was the issue. An easy work around was to place the effect at the bottom of the effects control, the comp should then render out fine.
Hope this helps, cheers.
Using OS X 10.7.1 on an iMac 27″ 3.4GHz Intel Core i7 + 16Gb 1333Mhz DDR3