Animation with DoF causing crash.

Hi, Ive come across a problem with my setup for some reason. I have a 5500 frame animation that renders correctly. Ive recently added some DoF (Depth of Field).
Single rendered images are fine,
… but when I try rendering the whole animation blender gets to the 120th-ish frame and closes. Sometimes it closes without saying its encountered a problem.

Am I likely to be doing something wrong in the way I`m using the DoF, the single rendered images I try are always fine though.?

I`m assuming the DoF post process is applied at the end of each rendered frame?
Am I likely to be exceeding memory somewhere?

I haven`t altered the user prefs at all apart from upping the memory cache to 1024 (max).

Thanks in advance, if any other info is need please just ask.

-Daz