Can I sue the mortgage lender if they back out after the commitment letter has been issued?

"Foreclosure Defense" seems the closest to my case which is mortgage lender backing out after commitment letter because of their mistake. Any help would really appreciated! My mortgage lender issued me the commitment letter, but backed out one day before the closing day. They said the condo has a pending "slip and fall" litigation of unknown claim amount, and the Fannie Mae guideline requires an exact claim amount for any pending litigation. Can they legally do that? Their commitment letter states: "The Lender reserves the right to terminate this commitment prior to the settlement of the loan in the event of any adverse change in your personal or financial status, or the improvements on the property are damaged by fire or other casualty." Not knowing the amount of the pending litigation doesn't fall into any of these events, and it's their fault not discovering it before the commitment letter. Now the seller has received the commitment letter from the lender, so we're obligated to buy the property but the lender won't approve our mortgage. Isn't the commitment letter legal-binding? Can I sue them? What kind of attorney can defend our case? We're pressed for time, so any help would be greatly appreciated. Thanks a lot!