Live Preview not working Live Preview isn't working for any kind of entry. Dev or production. I get the following error on chrome's console.

jquery-2.1.1.min.js?d=1409764106:4 
POST http://undiario.dev/ 500 (Internal Server Error)

jquery-2.1.1.min.js?d=1409764106:4 
k.cors.a.crossDomain.send

jquery-2.1.1.min.js?d=1409764106:4 
n.extend.ajax

jquery-2.1.1.min.js?d=1409764106:4 
n.(anonymous function)

craft.js:10520 
Craft.LivePreview.Garnish.Base.extend.updateIframe

jquery-2.1.1.min.js?d=1409764106:2 
n.isFunction.f


Anybody knows why this is happening?
Just want to mention for anyone running across this thread that if you're having a problem with live preview and seeing dev tools errors of the nature of cors or crossdomain then the first thing you might want to check is that if the domain you're serving the site (the control panel, specifically), is the same as what you have set in "Settings | General Settings" (or in Craft 3, "Settings | Sites")

For example, if you serving the site from a example.com (root domain), and you have www.example.com in the settings, your live preview will bonk because it's a different domain and the live preview is being served via ajax.