Hey - thanks so much for posting this, it has helped me tremendously tonight
(5 months later, with JVC GY-HD101).
I was already giving up and had no idea where to find an authorized JVC dealer here in Nairobi. After reading your post I tried the "tape massage" trick. While it could still not be ejected, at least I got the camera to play the footage in VTR mode, and I played it out to my hard disk.
When the tape was at its end... the camera unloaded and ejected it.
As I found out, the problem is the cassette: The plastic part in front that protects the tape is sort of dislocated and blocked the camera mechanism from unloading.