I've had three import Sega/Stern machines (LOTR, JP LW and Sopranos) and all had problems with the ballasts.

I don't know what voltage the lights are on an Australian delivered machine, but the American domestic machines are 110V even after you have converted the machine to 240V. The ballasts in these machines are a straight 110V 60 Hz, not 50/60Hz.
Australian ballasts for normal fluros are 50/60Hz but not the ones for Sega/Stern pinnies.

Each of the three machines I've had worked for a short period before the ballast blew and have worked fine since installing the 110V 50Hz replacement.

I am an Electrician and have experienced issues with the whole 50/60Hz thing before, but don't take my word for it, leave the ballast as is and let me know how you go.