Insert function of Fields does not work

Hi there,
I have a problem when inserting fields (date, page, time…) into my document in LibreOffice writer 4.1.5.
Instead of showing the date, time, or page in my document, what I got are Date(fixed), Time(fixed) or Page(Number).

However, when I copied those text and pasted them into this website (when typing my question), all appear as 04/07/14 and 12:33:09 AM, which are correct date and time I want for my document.

This problem has happened since I installed Colwiz.
I’m using elementary OS Luna based on Ubuntu 12.04. The language is US English.
Does anybody know why this problem happens and how to fix it? Thanks a lot in advance for your help.

Ctrl-F9 or View->Field Names will toggle between the field name and field content.