HID ballasts may take a tiny surge but nothing like a starter motor, think abut it, if the HID ballast took any thing much in thre way of current the wiring would melt, this is 12volts don't forget and very high currents are drawn by the starter motor. This is why it has such thick cables. If ballasts
took anything more than a minute curent it would also have massive wires to it. In other words absolute rubbish, the battery is nakard or you've disturbed some dirty connections whilst doing the installation.
So have a look under the tank.
dave gs.