After Effects CS6 render error - grey artifacts

Hi there,

I was wondering if someone could help me? I am rendering out a video in After Effects using H.264 codec, High 5.0 Profile at CBR 5 and 25fps. However, on all occassions and with all videos, not just this one, when the video renders, many frames appear grey (see below);

I have tried rendering it out at various levels of quality, both CBR and VBR, and even using Adobe Encoder also, and the problem still persists. It is not always in the same place also and appears randomly. I was wondering if anyone else had come across this problem and had a solution?

I have re-sintalled the Adboe Suite on several occasion to try and counteract this, but again, the problem presists.

Any help would be greatly appreciated!

Thanks,

Ollie