A potential warning sign from a peer It's been an awful, horrible, lousy year so far for UnitedHealth Group (UNH -0.22%). If I opened a thesaurus, I could easily find plenty of other apt descriptions for the healthcare giant's performance over the last seven months. However, UnitedHealth is scheduled to report its second-quarter results in just one week -- before the market opens on July 29. This update could be a pivotal moment for the company. Should investors buy the stock before July 29? Low expectation ...