Corporate Liability Protection? Maybe.
Many people understand that a corporation or limited liability company can provide its individual owners with protection from the debts of the company. For example, if a company is unable to pay its vendors, those vendors are typically unable to go after the owners of the company for those debts. Or if the company borrows money, the lender can only recover the debt from the company and not the owners/shareholders/members, generally.
However, if the owner of the company has provided a personal guarantee to that vendor or any other entity that has provided money or services to the company, the corporate liability protection is meaningless at that point. Most guarantees don't require that the creditor look to the company first, but could look first to the individual providing the personal guarantee.
If at all possible, an owner should avoid giving a personal guarantee when entering into any agreements. Conversely, as a creditor, whenever dealing with a small business with limited operating history, you should demand a personal guarantee from the owner(s) of the company.
