Have you tryed the bulb vertical? I know it sounds stupid but the do make MH and HPS bulbs that burn in specific positions. When you say 100w you do mean actual 23w bulb that is equivilent to a 100w bulb yes?? Could be a shit package, defects happen. take em back to home dePOT and bitch but I wouldn't recommend saying what they are being used for. I use 2 of those work lamps both of which have Y's in them and run 2 23w bulbs each = 200w and no problems what so ever but I also run GE "Daylight" bulbs.