My camera has this problem since ever, sometimes when I turn it on there's a system error and a message saying "Turn power off. Turn back on later" (manual, page 86). I sent it to JVC's service, they updated the firmware to the last version and the problem remains. I wonder if there are any other cameras with the same problem and what can be done to fix it...

Diogo, that problem usually only happens when you make changes in the format, rate, output, etc. within the menu, and the camera requires you to restart. That's what it sounds like to me.

It doesn't happen when I make changes within the menu, just when I turn it on. About once in each 10 times.

It sounds like it needs another repair. Mine never does that, except when I change from 25p to 24p.

Andrew