Change at-will status

I was employed as a salesman for seven years at a large O&G company that is an at-will employer.

I managed several customer accounts. In 2002 a contract was up for renewal and I put a bridging agreement in place in Oct. 2002 because the contract was ending and we had not finalized the new deal. On Nov. 11, 2002 the employer sent me an email stating that I was to spend 100% of my time on the account until the contract was signed. On Dec 10 I gave the customer what would be the final contract. The CIO was out until end of year. On Jan 15, 2003 I sent an email to management stating the contract would be signed in a few days. The next day I was fired. However I was paid severance and vacation. My commission was not paid but the contract was signed on Jan 26. Customer has given and affidavit stating that we were working in good faith to get the new contract signed. Employer sent a mail stating I was fired because I did not bring this contract in and that I was given more than 3 months to do so.

Did the employers email change my at-will status? If so, the 3 month rule is not correct. Do I have any recourse?

Thanks,