Before I went to Florida, I had wired a 8' fixture and the ground what touching the fixture itself but not the ballast, the ballast is magnetic. I tried to turn the fixture on and all I got was a partial discharge. When I conneted the ground to both the fixture and the ballast. The result was perfect and the lamp started up.

But why does it have to be properly grounded in order for the fixture to work? I know this isn't the case with some fixtures but some do need to be properly grounded.

In rapid-start installation, the reflector of the fixture or the fixture body itself, is used as a starting aid antenna when grounded, since the OCV of rapid-start ballasts is very low (200V). This isn't needed for preheat, instant start and other ballast configurations, where the grounding there is only for safety.