Hate to drag up an old thread, but I'm having the exact problem... but with the 24" fixture. Based on the Amazon reviews, I'm not the only one. Strangely, my 30" has been running happily for four years... knock on wood.
I had 24" fixture for about 6 months and was happy with it. So much so that I recommended it to my parents when they started up their 20 gallon. Big mistake, by the way! Within a week of having it, theirs failed in a spectacular fashion - smoke, fire, and melted plastic fused to the top of their tank. I felt terrible for possibly inadvertently nearly causing them to lose their house.
Of course, I felt even more terrible when mine failed a few days later. Same issues described in the thread: bulbs have blackened ends and only flickered when turned on. I replaced the blackened bulbs and it worked again, but only for a week or so. At this point, I'm not really willing to waste any more expensive bulbs on a faulty fixture.
Just wanted to point out that the 24" Coralife T5NO has issues too.