I had a similar problem with a Sony Camera (Different Error code obviously). I fixed it by removing all power when the camera was in Play/VCR mode. The manual suggested that removing all power for 60 seconds (camera in Off position) will do the trick, but it didn't. Apparently removing all power for 60 seconds whilst in Play/VCR mode discharges the internal circuits. Don't know if JVCs are the same or not, but certainly worth trying before giving your Cam a hefty bunch of fives.
Turns out head cleaning didn't work, and all tapes are playing in the way described in the first post, ie not really working. The camcorder is a JVC GRD31EK and it keeps coming up "Error EO3 Unit in Safeguard Mode. Please eject and reinsert the tape
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
Sony TRV33e : Sony TRV310e : Canon XM2
Sony Vegas Studio editions to v11
Remember, there is always more to learn than there is to teach.