Moderator Post (s) for this thread: >Check plug alsobyDanO on 11/23/2008
You have a bad connection.
It can be in the receptacle. It can be the connections to the receptacle. It can be connections at an upstream box. It can be connection in the panel. It can be the breaker.
Most likely it is that receptacle, specially if plugs are loose in the receptacle or the connections at that receptacle.