The older ballasts can and will get fairly warm, but they're not supposed to get "super hot". When they do, there might be cause for alarm. Here's an old trick for an old ballast: take a strike-anywhere match, and touch it to the hottest point on your ballast. If it ignites, don't use the ballast! Get it repaired by someone who knows what they're doing (especially if it's still under warranty), or just invest in another ballast altogether. It's much less expensive to replace a ballast than it is to replace a burned down house! Especially when you consider that most insurance companies won't cover damages made by using a faulty ballast in conjunction with the cultivation of an illegal substance.

Another thing to consider...if you take a small fan, set it to its highest setting, and have it blowing directly on the ballast exhaust vents (which most ballasts should have), you'll be able to keep it much cooler than if you had no air circulating around it at all. My old 400w HPS ballast used to get pretty warm...actually contributing considerably to the overall temperature of the room...and when I trained a fan solely on the ballast, the temperature of the room noticeably dropped. I do the same thing with my current 1000W HPS, and never have problems with heat coming from the ballast itself. I'm finally about to invest in a digital electronic 1000W MH/HPS ballast, and will soon no longer have to worry about ballast fans at all. Can't wait!

Good luck, and be careful.