[Monkeydad]

Here's a better source that says a little more than "Malcolm Kelly got hurt":

Redskins Insider - Malcolm Kelly injures hamstring at Donovan McNabb's 'Hell Week'

Kelly experienced tightness in his hamstring during one of the workouts, the sources said. He immediately contacted the Redskins' medical/training staff for guidance. The Redskins plan to proceed cautiously with Kelly, who worked hard to overcome knee problems and microfracture surgery after his rookie season. Coach Mike Shanahan is expected to address Kelly's situation after the first practice Thursday.

Although the injury is not considered serious, the team would rather have Kelly rest and receive treatment than try to participate in the early stages of camp. Hamstring injuries can linger, especially when players rush back before they are completely healed.