Also my Ubuntu don't boot anymore. I already installed the package at-spi2-atk with no avail. I think this package should install that lib on my system. I don't know if it's related to the boot problem, but i'm guessing it is.
Thank you for those who tried to help me out.
I accidentally mistyped the ubuntu version. It's actually
Precise Pangolin version.
Anyway, I had it upgraded to 13.04. I'll still try to reproduce the issue later on though. So if anyone has a recommendation, please reopen the the question. Thanks.