Unless the globe is shattered my vote is on the ballast as being faulty. At least that has been my experiance over the last 8 years with HID units. Bulbs are almost universally made well, ballasts are a crap shoot. Buy cheap get cheap. I had flicker and starting issues I struggeled with until I changed my 7 year old crap ballast (it worked real god for 4 years) with a good Phillips unit I picked up at an auction. Same bulb (8 years old) now fires every time and reaches full brightness rapidly.