ORIGINAL: MrMikeG

1. Plug like Matt said, the resistors do go bad in them, esspecially Champions! I believe it's a Champion.
2. Check for water and corrosion in your servo's, reciever and connections, any green spots replace. Will do.
3. If your servo's aren't in the radio box they need periodic maintanance, and resealing so they don't get wet. Given the throttle servo's relation to the rear opening of the hatch, I think you may be on to something here.
AM radio's do get interference from electrical noise or metal to metal rubbing. (any brand) FM is better in a gas boat, PCM even better and the NEW 2.4 ghz are proving to be good too, beware though the first 2.4 ghz radios out were bad, lots of range issues.
How far away was your boat when you had problems? Anywhere between 30-60 yards. Do you know how to range check your radio? I did last year when the batteries were new to check the failsafe. Seems it was close to 100-120 yards. I'm not quite sure, but it was a lot further away than I'd be comfortable trying to control (or even see) the boat.What kind and how many batteries are you running in your boat? They're GE replacements from last year. I think there are six in the holder. They're AA size I believe.
Please don't let people swim while your running, especially if your having radio problems. Not a chance. In fact, I even waited until there was no boat traffic either. I'd hate to be driving the torpedo.