Did you and/or the buyer use Realtors? What about your attorney? That seems pretty odd that they would do that. If they built some type of contingency into their contract, it may be difficult to get them to perform, but they may risk losing their deposit as well. Definitely consult your attorney and have him/her reivew the terms and conditions.
Best of luck to you.
Charlene Weston (Cobelo)
Smith and Associates Real Estate