It is almost impossible to shoot this lens in the nighttime for me.
I know what caused this problem...
I bought this lens really cheap because it had a scratch on the front element. I was fine with that, but I didn't know it turned out in such flare disaster.
Lots of (commissioned) pics are worthless now.
In the daytime I have no problems at all with the lens. I guess I have to wait for the new 14-24 or 16-50 IS