I still stand by what I told you in the PM... not all MV ballasts will properly run halide lamps, even of the same wattage. If the ANSI code on the ballast does not list an M designation, then it's not designed to run a halide lamp.
That doesn't mean it won't light up; it may work anecdotally. However, IMO since the right ballast is like 40 bucks (or about half the cost of a decent halide lamp), it's worth it to not risk the lamp and use the correct ballast.