How old is the ballast? If it's past it's warranty, you might still be able to send it to icecap and they can refurbish it.
I've never had an icecap, but it sounds like it is tripping off from heat. Try putting a fan on it to see if that makes a difference.
On a side note, is this hooked up to a timer? Try plugging the ballast in direct. It could be the timer messing up as well.