Posting sourcecode not works on wordpress 3.5

I´m trying to use:

[sourcecode language="css"]
your code here
[/sourcecode]

It´s documented here: http://en.support.wordpress.com/code/posting-source-code/

I´m using Twnety Twelve Theme, but nothing happens when i add the sourcecode tags. I tryed to paste code in Visual editor on Text editor and always the same null result the tags aren´t parsed.

I´m desesperated dont know whats wrong….