GV4 VW - I have the exact same problem with my OEM xenon retrofit. The bulb error appears when ignition/engine is on, lights off. However, when manually turning the lights on, the bulb error disappears 99% of the time. However, sometimes, one of my xenon's fire up but the other doesn't, again causing a bulb error. This tends to happen when the light switch is on 'Auto' and the car enters a tunnel, turning the auto light function on, but only for one bulb! The bulb error is then eradicated by simply turning them off and on again, albeit very annoying.
My car is a 1.9TDI SE, I know a guy who has the same model of car, with xenons and he has a similar problem with the bulb error when lights are off, although he doesn't appear to have the problem I have with only one coming on when going through a tunnel with lights on 'Auto'.
I believe upgrading to the latest Canbus module/gateway may potentially solve the problem, although I'm sure someone will correct me if I'm wrong...