I'm not the one with the cat related problem. My cat does not go anywhere near any of my rigs.
As for hedgehogbrown. He will have to come up with a better plan, as the problem is not only "cat on top of case". As I see it, the two best solutions are:
A: Isolate the case. Cupboard, basement or similar. As long as it is somewhere the cat doesn't go.
B. Find or make a case that is "cat-proof". In this case that means waterproof (as much as possible) and easy to clean.