A complaint was filed yesterday in Chancery Court by the above named parties regarding a "deal gone bad" as reported here on The Wall Street Journal Law Blog. The comments below The WSJ Blog post have links to the actual complaint.
UPDATE: Here is a press release about a separate class action filed against United, claiming that they should have disclosed sooner their awareness that Cerberus expressed reservations about closing the deal. Hat tip: Kevin LaCroix of The D & O Diary.