Well I can tell you for a fact it has happened to me twice now.

Flying my helicopter in a remote farm field. Flew straight down the runway and the bird glitched. Nothing big just a jump up and down. Landed and checked everything over on the ground and everything seemed fine. Heard a beep and noticed that my cell phone, which was on my belt at the time had recieved a text message. I didn't think too much of it but 2 days later it happened again, after I landed I noticed I had recieved a call while I was flying. In both cases I was the only one at the field with a transmitter. It wasn't enough to cause a crash but it was definately due to rf interference from the cell phone being in close proximity to the transmitter.

This was with 2 different heli's, 2 different recievers but both use the same 9C transmitter with a crystal module.

Before anyone says I have no idea what I'm talking about, I was a radio communications operator on a P-3 as well as an avionics and radio technician in the Navy working on everything from HF to microwave and satilite communicatons systems, radio teletype, encrypted com's etc for 12 years.