Sounds like a typical 400 watter, the biggest issue people have is that they cram a 400w hid light into a small area.
The general overall temp of the room is the issue not the temp of the bulb, an 400 watter could be as close to 10" with out any type of cooling, with a cool tube u could be pretty much right on top of the canopy give or take a few inchs. The bulb itself could be the issue too, not the ballast. You could look into what bulb they gave you.