Login With Facebook Button Disappear

Hi, first of all sorry for my bad english...

I've updated my wordpress recently to 3.4.2 version. On the prior version 3.4.1, the login with facebook button showed well, nothing wrong, but I have no idea what makes this disappear now... I use Cloudflare as CDN and W3 Total Cache as my Wordpress Cache Plugin. I've tried to switch off both of them (the cloudflare and w3tc), but still confuse here, the button is still nowhere to be found. Any suggest here?