I bought not one but two JVC GR-D33US and both stopped recording video. The first at 6 months of use and the second at 8 months. As in your case, the screen just stays black; while playback works fine.
Have you tried to get some information at www.jvcservice.com?
I don´t because I live in Venezuela and its too expensive send the camcorders to US.
Anyway, if you receive any hint about the specific part that gone bad in your JVC, please post-it so I´ll try to get it from some retailer in my country.