I have made some progress with libgphoto2 driving my DSLR without going belly up. I have modified CritterCam such that the DSLR does both the preview and the motion activated shots and it has been stable for the past ten minutes (previously it would only run for less than a minute before going boom).
Here are the changes that I made:
These are courtesy of the Raspberry Pi Forum and user elatllat. This forum rocks in terms of helpful and responsive feedback.
I do still have a bit of an issue with the method that I am using for motion detection but I am hoping it is because of the conditions within which I am currently testing (indoors without a lot of light).