Cheap fixture? (Not a name brand electronic ballast)
Cheap bulbs? (maybe same lot or batch as the old one?)
Cheap ballast? (Same deal as with bulbs)
Grounding of the fixture can be an issue...
So can low available input voltage...
All of the above...
Then my favorite... improper burn in time of the lamps. Try leaving them on for 24 hours or more for the first start up, it helps... It is actually required for dimming lamps, but have noticed a difference in non dimming...
