SKuhn68,
I used 72 MHz right through last summer with little to no problems, on larger nitro planes. If you want to make sure its the receiver, try and take the receiver out of the plane and hold it away from the model while running it up, as we did with the club members plane I was speaking about. If distancing the rx from the electronics in the plane make your problems go away, you know a couple different things. either A. if possible you need to move the receiver way out of the way of all of the other electronics, or B. you need to upgrade to the 2.4 system.
I didn't take the reply as unappreciative I totally understand your frustration!
One way or the other I'm sure you'll get this model squared away, your doing the right thing by asking for advice and working to get the issues ironed out!