Check your battery connection, make sure it's tight and clean. There may be a small bridge in there that allows lights and what not to work, but the current draw of the starter is too much.

When you jump the car, it may be crimping the battery terminal tight again, but it loosens over the next couple days driving.

If if I remember right, the battery clamp on those is pretty thin and prone to stretching, making it loose no matter how much you wrench it down