HELP! Can a hosiptal cancel your contract after you have signed??

Hi guys!

My question is about contracts being canceled. I have gotten myself into a horrible position!! I left my job to start traveling and I had an assignment that was suppose to start 1/9/09....well on 12/31/08 they called and told me that it was canceled due to 'low census'. I was soo upset and had no idea what to do.

A week later I got a call from my recruiter saying the hospital would like to offer you the same position again because census has gone up. I was thrilled but still skeptical. Well I am suppose to start 1/23/09 and I signed my contract last week on 1/8/09 and today(1/13/08) I got a call saying that it was being canceled. Except this time they are saying it is because the nurse manager called me and I told them I wasnt interested in taking the position anymore (HOWEVER, I NEVER RECIEVED A CALL FROM THE NURSE MANAGER...EVER!!). So, basically I know I am being screwed around with.

So, my real question is...what is the point to signing a contract if it can be canceled at any time?