Help please ~~~

I've installed the FEC module for my zen cart (1.3.9h)

Everything working fine until i have modify certain wordings in the zones.php located in language folder.

When i clicked on check out,

the page show blank with the url (index.php?main_page=checkout) instead of the normal (index.php?main_page=checkout&fecaction=null)

Anyone has any idea how to solve this issue?

Many Many Many Thanks