default on loan agreement signed under a corporation, can someone be personally liable under FL contract law

The individual's personal liability will depend on the terms of the contract. You should have an attorney review the contract and also the lawsuit complaint. The plaintiff may be seeking more than they are entitled to.

The simple answer is YES. It is not uncommon for lenders to require that an individual also guarantee a loan to a corporation, particularly when it is a small, closely held corporation. The only way to know tha answer to your question is to read the loan documents.

A corporation, by definition, provides the owners protection from corporate liability, including corporate debt (unless, among other things, fraud has occured). However, as some of the other attorney respondents have noted, a party may (and often do) waive this protection when entering into a loan for a corporation and are thus held personally liable for the corporation's debts. This waiver is called a "Personal Guarantee". A thorough review of your loan documents and a consultation with an attorney is highly recommended.