I have also been shocked by this type of metal halide fixture and survived. It was a lesson in proper testing for live circuits for me. These fixtures have large ballasts and are often in hard ceiling areas of buildings. So changing the ballast is difficult even when the power is off.
An option for this fixture type is to have a current sensing relay that turns on a 120 volt E-power fed quartz lamp if the metal halide lamp fails. The relay is often contained in a separate enclosure which has only 3/8" flex grounding it. When I checked for power, I did not notice that there was still emergency power in the relay enclosure. OOPS! Big shock.. Because of the double sources of power and the confined work area these fixtures are very dangerous.
It now makes sense to me to replace these death traps with a compact fluorescent fixture--cheaper than a metal halide ballast and much safer to work on!!!
