Very interesting flash =)
This actually made me think! Murphy's law states that anything that can go wrong will go wrong, while cats land on their feet because their instincts and abilities help them to do so.
So you have a really complex situation here. If you don't want the toast to land on its buttered side, it will. But the cat wants to land on its feet, so Murphy's law dictates that the cat will fail to land on its feet. And the aim of the experiment will be to have the Murphy force and the Cat force to cancel out so none of them land. But Murphy's law will act on the experiment too! So no paradox will form, the toast lands on its buttered side and the cat lands back first.
But if you UNINTENTIONALLY throw a cat and buttered toast out of a building, and was not even aware of what you did, then there would be no intended outcome for the Murphy force to influence, and SUDDENLY CATS EVERYWHERE OHGOD