I just purchased a gv800 and had the exact same problem. After reading several posts in the forum, I was convinced that I had purchased a clone. Tried everything, new cameras, new video card, new computer, formatting, power supply. The problem turned out to be bad cables. I made the cables myself using crimp-on connectors. I cannot believe the cables I made were that bad. To test I purchased a cacle from RatShack and now everything works perfectly. It may be worth a try for you.