Anytime you use any high frequency device with a long cable (ballast,welding station,class D amps ect) it will create some type of noise from the output, this is normal and if you put it near any type of network that also oscilates at the same/similar frequency range, it can interfere.
The amplitude of noise will depend on the quality of the cable, shielding/quality of the ballast's digital power supply & orientation/routing of all signal cables.
So the next guy to have this problem, you should carefully plan your cable route away from other signals, use good quality cables and always coil up your slack to help bleed off the remaining EMI.