My Siamese cat is always biting my Great Dane. I didn't think it was much of a problem, because the dog is a giant and he just never really reacted to the biting, just kinda sat there. Today though, his foot started bleeding :(. How can I get the cat to stop?
It sounds like the cat is afraid of the dog. Is the cat able to go outdoors when it likes? If not, it will feel trapped, and this may be the cause of the problem. As @M.Mat implies, some perches that the dog cannot reach would be a good idea. A box that the cat can hide in and get some privacy would also be useful. You may need need to feed the cat separately, either in different rooms or at different times. Dogs have a way of barging in on other people's meals. The cat will interpret this as bullying.
Of course, the cat may just want to play. Does it hold its tail straight up when it interacts with the dog. If so, this is a sure sign that all is well. Even if this is the case, your cat still needs a retreat from the world--a place where it can feel absolutely safe. Get it some perches and a little hidey-hole.