Animation render problem - PLEASE HELP! URGENT

I have a scene in max 2014. It's a 660 frame animation with some complex product models in it, the camera pretty much remains static and the product moves, it's a promotional video for a big phone manufacturer.

My problem is: if I render 1 frame (let's take the busiest scene) at full HD (1920x1080) it takes around 40 seconds but I want to set them all off. If I use the animation frame buttons in the normal max render setup solid rocks tells me I shouldn't use the render button and render time increases massively, if I use the anim full button within solid rocks, solid rocks starts off fine but by about frame 50 render times go up massively. For example, if I render frame 100 on it's own, it takes around 40 seconds, if I set the animation off by the time it got to frame 100 it was take around 40 minutes per frame!!!

I have a client waiting for this work, I've told them I have a technical problem but would love to get an idea from anyone on how I can just render each frame on it's own over all frames i.e. An animation!!!

Please don't ask me to supply the scene so you can see it, it's under NDA, would just like to know anyone's thoughts, see if there's anything I haven't thought of, thank you

Windymiller73