Marc hit the nail on the head!
Halogen Lamps have what is known as "The Halogen Cycle", which should be known for extended Lamp Life.
Simply put, to get the most life out of the Lamp, keep it as Horizontally Level as possible (+/- 4°).
This causes the Atomized Fillament to land back on the Filament, during operation.
When the Filament fails under load, the Atomized material allows an arc to be sustained, and the Arc has no Resistance (actually has negative resistance) - so there is a large increase in load current, which trips the breaker.
Same would occur if any Non-Ballasted Discharge Lamp was thrown across the line.
Scott35
