Ok, from what I understand, the ballast is grounded only by way of the housing.
I cannot tel by the spec sheet, if the ballast has a ground lead or not. Or whether the bolting to the housing is the ground location.
So, if the ballast has a ground lead, please connect the ground wire to your ground wire for the fixture, not through a screw and paint etc.
If it doesnt have a lead, then please use a wire and connect tot he ground on the fixture and then to the screw holding the ballast in place.
Need to test and see if you actually have a ground with a tester also. Measure between the hot and the ground and see if you show 120 volts.
This will insure a ground and we can troubleshoot if needed, at least knowing the ground is getting sufficient connections.
You would not believe how troublesome some of the electronic ballasts can be on grounding.