Or since Futaba receivers are high or low, you could have a friend put in a compatible receiver crystal in your receiver and range check your plane to ensure it is not in the airplane.
Basically, thats what we did. We took the crystal out of my Tx, and dropped it into a different Tx (both Low band, one channel apart). We then range checked it and had absolutly zero problems. This pretty well convinced all the experienced folks watching that the issue was in the Tx, not the Rx or servos themselves.
So, three weeks from now (hopefully) we'll have our answer. I'll be sure to post an update!