I will have to look at it, but it runs to a certain date, requires notice of termination and I imagine there has to be something in the law that governs a contract being signed with someone else that supersedes yours and replaces it- ESPECIALLY before mine is even terminated. I was told about it AFTER the fact. Some kind of competition clause, law or something. Especially when you are being replaced.
In general, there is the freedom to contract. There are very few laws which govern the substantive content of a contract. If you want to create contracts with two different people to do the same job, then you can choose to do so. Now, there are a certain number of things that can void any contract, but what you are talking about is not one of those things. There is nothing against the law about signing a contract with two people at once to do the same job. As AWK mentioned, it all depends upon what the contract(s) say(s). If there is an exclusivity clause which prevents them from contracting with anyone else before terminating you, then yes, what they are doing would contradict your contract.
Also keep in mind that with contract law, the remedy you're going to get is only going to compensate you according to the terms of the contract. If they are to give you two weeks notice and two weeks pay before terminating your contract, yet they don't do so and instead immediately terminate you, then a court is probably only going to award you two weeks of pay for the breach of contract. The goal is to give you the same benefits (or as close as possible to the same benefits) as you would receive under the provisions of the contract had it not been breached. Don't expect punitive damage awards based upon intentional infliction of emotional distress or anything extreme.