Co-Signer won't let me sell; Help?

I have a home I bought with my ex boyfriend. I am the owner and his friend is the co-signer. I have had 2 buyers and the co-signer said he wouldn't sign it over to either of them unless my ex said it was ok, my ex said NO to both buyers. So I am stuck with this house...should I foreclose? or is there any other way out of it beside spending tons of money in court?