Might be your electrical, could be too much humidity, could be the wrong bulb for ballast, could be a number of things..... Sometimes when too much electricity is available to a bulb, your bulb can and will burn out. So it wouldn't be a good idea to put a 400 watt hps bulb in a 1000 watt hps ballast. Know what I mean??.....

The best advice for you would be for you to get an actual grow lamp so if you still have these problems, at least you have a manufacturer that you can call to help you trouble shoot.