ORIGINAL: IL_BOW_MAN
As I am not sure how the camera is setup inside the box, one guess of mine would be to check and make sure the flash is sealed off. If it isn't the flash could be bouncing around inside the box.
Ok I agree with this being the most possible problem.. Another thing to check is the battries.. I recomend that you be using Lithium batteries as they do not freeze as easily as the rest. I think they are rated to work or not freeze until -35* without windchill.. I work on IC's alot and deal with electronic's and I think that IL_BOW_MAN is on the right track.