I've been running the C50 for months now and it usually locks onto satellites fairly quick and remains locked. I purchased a new Kodak Zi8 video camera and use the supplied power cable going into the cigarette lighter instead of the batteries. If the power cord is powered up and plugged into the camera, the C50 cannot track satellites. With the camera plugged into the cigarette lighter outlet (and powered up), I reset the C50 and even after five minutes, it was unable to obtain satellite lock. As soon as the camera is unplugged, it locks in less than a minute.
I also tried another car dvr camera system that plugs into the lighter outlet and the C50 is unable to lock satellites with that one as well until it's unplugged and powered down. I attempted to try this with a Garmin Zumo (Nuvi) and it appears to have a full strength signal even with both cameras connected to the lighter outlet.
It seems like it's definately some kind of interference when using a camera but can't tell if it's something screwing up the incoming 12 volts to the C50 or something emitted from the cameras.