problems with my HID kit
 

I just had an HID kit installed in my 04 clk 500; the problem is that my headlights only work sometimes. At night the headlights come on automatically but as soon as I switch on my fog lights, the main headlights turn off. When Ipull my car out of the garageand turn the headlights on, they work but as soon as I drive somewhere and turn the car and lights off, the next time I get in the car and try to turn the lights on, they don't work. Is my car overheating my HID kit or are my ballasts faulty? The kit is only about 2 weeks old, so I don't understand what the problem could be...can someone please help me???