That's one thing about the electronic ballasts I don't like. I think only Icecap as far as I know, makes it so that their product is serviceable. Any others with this epoxy coating idea and you're S.O.L. Had it happen to me, spent $250 on a ballast, got 5 minutes of use on it until a short in the reflector wiring caused one of the lamp leads to ground out. Says right on the ballast "DO NOT CONTACT LAMP LEADS TO GROUND". All I could do in the end was throw it out.
I'm still bitter over that one. I steer well away from electronic ballasts, the five cents per month savings you might get on your power bill will have to take a long time to recover the premium you pay for buying electronic in the first place and it will never reach the point where it pays for a lost ballast like that case. At least in your case it is still working .. kind of .. so find another lamp and see if the problem goes away. My money is that it's the lamp and not the ballast in this case.