Well, in my opinion the there is no simple “yes” or “no” answer. Because first you need to define what you understand as “happiness”. If think about some temporary emotion, than yes, money can buy it. I experienced this several times in my life when I bought something I dreamed about. I still remember the pure bliss, for instance, when I bought my first really good stereo and put the first CD on. Or the first ride on my first mountain bike. First ride in my first car…etc. I really felt happy in those occassions.
If you are thinking about happiness as rather permanent state of mind, well, if something like that really exists, I doubt money have much to do with it. They can help, sure, but they can spoil it as well. So no – this kind of happiness is relative to everyone’s expectations, values, attitudes etc.