The oDesk terms provide,
Quote Quoting 13.12 Informal Dispute Resolution and Arbitration.
oDesk and User hereby agree that any Claims shall first be settled through the oDesk dispute resolution program. Claims that the parties cannot resolve informally and where the amount in controversy is less than USD$25,000, the parties agree to resolve the Claims in a cost-effective manner through binding non-appearance-based arbitration conducted by a single arbitrator. If a party elects arbitration, that party will initiate the arbitration through an established alternative dispute resolution (ADR) provider mutually agreed upon by the parties or the American Arbitration Association (AAA) if no other service is agreed upon. The arbitrator shall be selected from a list of no less than five names through alternative strikes. Unless the parties mutually agree otherwise, the ADR provider and the parties will proceed as follows:
a. the arbitration will be conducted by telephone and/or be solely based on written submissions, as specified by the party that initiates the arbitration;

b. the arbitration shall not involve any personal appearance by the parties or witnesses; and

c. any judgment on the award rendered by the arbitrator may be entered in any court of competent jurisdiction.
Disputes over $25,000 that do not involve oDesk may be resolved in whatever forum the parties deem appropriate. The California state courts of San Mateo County (or, if there is exclusive federal jurisdiction, the United States District Court for the Northern District of California) will have jurisdiction and venue over any Claims where oDesk is a party and the amount in controversy exceeds $25,000; each party hereby irrevocably consents to the personal jurisdiction and venue of these courts. This Agreement does not prevent the filing of charges with a government agency like the Department of Labor or participation in any investigation or proceeding conducted by a government agency.
You can explore with a lawyer in your undisclosed state (or country) whether your jurisdiction's laws provide you with a way around the arbitration provisions or the choice of venue clause. Or you might want to take advantage of the arbitration clause. I don't know if the amounts involved in your dispute would justify the costs.