But thats not where the story ends: All my XCode Project, yes... ALL of them is not working. It couldnt be compiled. And it gave me some fancy errors such as "cannot find Math.h" in a line where I include C++ built in library, math.h. If you notice, I use a different M. Its not typo, but it is what happened. There are also any other errors that I even can't read what those are.
The solution: Re-install your XCode. I'm not sure what happened, but everything seems to be working again after I installed my XCode. Its kinda weird since all I did is to re-install my Snow Leopard. Its the same system. But probably I did miss something.
Hope this helps.