An intermittent heat problem with a receiver crashed this model airplane.
Receivers contain surprisingly sophisticated electronics. This is specially true of the newer 2.4 GHz spread spectrum receivers. I heard the story recently of a model airplane that experienced an intermittent failure. The problem was eventually traced to an overheating receiver. In the heat of the midday sun, it would just stop working. Once it would cool off, it would start working again. It was one of the newer spread spectrum units.
There are two major sources of heat in our electric model airplanes: the motors and the speed controls. The motors are usually out on the nose isolated from the rest of the components. What you really have to watch out for is the heat from the speed controls.
Electronic speed controls generate a lot of heat. That heat and sensitive receivers simply do not mix. Keep those two well away from each other. Make sure both of them get a generous amount of cooling air, specially if you fly on hot days. Think twice before completely wrapping your receiver in foam rubber. Foam rubber is also an excellent heat insulator.