There are only two options I can think of, either the lamp or the ballast. The momentary brightness and flickering might be due to the high voltage supplied to the lamp to strike the arc, then it drops to the normal operating level.
After BB replaced the lamp in my Samsung under the "Buyer Protection Plan" the new lamp lasted 1000 hrs then flickered and died totally. Turns out they used a counterfeit lamp to save money. I replaced it with an OEM lamp and all is well.
I guess the main problem is if you want to put money into a low resolution, 4:3 projector.