Buyer backs our stating mental condition

[Kim Proffitt]

What is the name of your state? Oklahoma

On February 15 we entered into a contengent contract for the sell of our home. The contingency was that the 2 individuals has to sell one or both of thier homes, one listed with an agent and one listed by owner. On March 6 we were presented with another contract from a couple that were prequalified, didnt have a home to sell and wanted to close in 30 days. We negotiated and came to terms at which time our agent contacted the other party regarding the contengency starting the 72 hour time clock. At the (11th hour) we recieved the phone call that the party with the contengecy had removed the contengency obtainning financing to purchase our home through the use of a bridge loan. The other purchasers were very upset that they had lost the contract on our home and went about starting a new search. We set a closing date for April 11 and moved forward.

On March 29 I received a phone call from our agent that the buyers were backing out of the contract stating that one of them had a mental condition (bi-polar disorder) and had been in a depressive state for the last 6 to 8 weeks and was unable to enter into contact. The agent faxed over the mutual release (which was signed by both parties including the one claiming to have the mental condition) Funny... another contract she cant enter into.
Which I might add ours is not the only contract she has entered into during this time.... she signed a listing agreement to put her home on the market, she signed a contract for financing etc. Ours is the only contract they are breaching. How can you pick and choose which contracts you want to enter into and which you dont?

We are set to go to mediation on the 29th of April aledging breach of contract and requesting specific performance becase they have impeaded the sell of our home.... I want justice from them and also from the real estate company which claimed to have brought a qualified buyer to the table.
Based on everything I have read so far most cases of specific performance are when the seller decided to back out.....

What are your thoughts and suggestions?