I have a two-bulb F28T5 light fixture that went out and replacing the bulbs with new ones did not fix it. So I replaced the ballast with a new one. The lights come on but go out within a second or so. I cleaned the prongs that hold the light with alcohol and a Q-Tip but that didn't help.
I bent the prongs inward slightly and then the bulbs stayed lit for at least five minutes, long enough that no one noticed when they went back out. I tried rotating the bulbs in their sockets again but, as before, they only stay on for a second and go out.
The only thing I can think is that, perhaps, one of the bulb holders is bad or loose but, with it staying on as long as it did before, I wonder if there's something I'm not thinking of.