Rental Renewal Letter

Does anyone know if a rental renewal letter is a legal binding document?  My lease expired on 1/29/12.  The property management company sent me a renwal letter back in November 2011.  I check the box on the renewal letter indicating that I would like to renew.  The letter stated that they would draw up a new lease, have me sign it and return it to them.  I went over to the management company 3 times during January to sign the new lease and they indicated that it was not ready.  On the 3rd visit they said it was still not ready but that they would send it over to my apartment for me.

It is now May and I have purchased a home and have sent a letter in giving 60 days notice.  The property management company is saying that I owe them the $1,275 cancelation fee from the original lease because the rental renewal document was my "new lease".  Is this legal?