Objects disappear for no reason in render with rigid body physics

Hi, I’m trying to make a keychain with rigid body physics but something is preventing my animation from rendering properly. When I get to a certain point in the animation, some of the objects disappear for no reason.
The key itself reappears, but I have no idea why.
Only the objects with rigid body physics applied disappear (the key itself doesn’t have physics, there’s a box holding up the smallest link in the chain which is hidden inside the key).

So I’ll be rendering it, then nearing 30 frames it goes transparent and then totally disappears. The animation should last 150 frames though!

Here’s a video of it in the viewport, where it seems to be working perfectly:

But then as you can see in this render, it does something weird.

http://i.imgur.com/aubPeCp.gif

I thought at first it might have been disappearing because I had changed the location of the objects as well as giving them physics, but they still disappear even when I only apply physics.

http://i.imgur.com/yyO7uOy.jpg
http://i.imgur.com/ukmeyh1.jpg

Can somebody please tell me what I did wrong? :frowning:

Sorry for the massive images, I don’t know how to rescale .gifs

Can somebody please tell me what I did wrong?
One thing you did wrong was not including a link to your blend file.

In the time it took to approve this thread I figured it out - I had to disable motion blur. That fixes it. Somehow. I also baked it but I don’t know how much that had to do with it.

Richard you definitley need an (provide blend) script