I used the internal component upgrader to upgrade from 1.2.6 to 1.2.7. Guess the internal upgrader might have some issues for upgrading. I've tried downloading the 1.2.7 installer and re-install over it. Now it's working like a charm!
Install the ES 1.2.7 launcher from the dashboard of stackideas. Then install it into the site, proceed with the installation. This should fix the problem.