Do you owe more than market value on your home? You may have options, one of which is a promissory note.
While not the best option, it may be possible or advisable if the balance is sufficiently low. (E.g., if you are 5,000 underwater, you may want to do a promissory note.) This MAY enable you to satisfy the sale and avoid the credit hit.
Always consult a Realtor, tax or legal professional as applicable!