i've been thinking about this for a bit. This is a very strange situation. If you had a serious short, i don't see how you could be blowing lamps because the short would go right to ground and wouldn't affect the bulbs. Then i thought the only way you could blow lamps on a circuit was if you were supplying more than 12V to the lamps, and this would cause them to blow, but not as serious as what you describe. Then i thought about your comment, i fired my truck. Is it possible that you have somehow wired your power supply wire for your lamps from your ignition coil? This would give you very high voltage and would cause a lot of damage. That's the only thing i can think of, is that you somehow hooked into your ignition circuit. Where did you get your power from for your lights?
Hope this helps.
"Well done is better than well said." - Benjamin Franklin (1706-1790)