In West Willow-Bay Court, LLC v. Robino-Bay Court Plaza, LLC, No. 2742-VCN (Del. Ch. Oct. 6, 2009), read opinion here, the Delaware Chancery Court discussed the theories of mutual mistake and unilateral mistake as a basis to reform a contract. After applying the facts and analyzing the issues, the Court, in a 16-page opinion, rejected the reformation arguments based on the circumstances in this case that involved a contract for the sale of a pad site and the issue of who had the obligation to obtain consents needed by third-parties for a proposed development.
Several prior decisions by the Court of Chancery in this case have been summarized on this blog here.