Look and see if it is just plugged into where the stock bulb should go or if wires are spliced and cut up. Is this both headlights flickering or just one?
PNP style will just use your driver's side headlight socket and then run a wire across to the passenger side. Two ballast will be used, one for each side. If this is the style, then check the all the connections.
Switch the bulbs and see if it follows the bulbs from one side to the other. Then switch the ballasts to see the same.
Edit: You need to fix this ASAP. The rule of thumb to follow with HID's is:
Do not turn them on and then turn them off within 5 mins.
Do not turn them off and then turn them on within 5 mins.
Do not use them for more than 3 hours at a time. After 3 hours, give them a 5 minute break.
HID's are made from a mineral that heats up when you turn it on and turns into a gas. You have to let it change from solid to gas each time you use it (10 min rule) or it will greatly reduce the life of the bulb.