Problems of multilanguage updating wordpress 3.0.0 to wordpress 3.3.1

Hi,
I need to update wordpress 3.0.0 to wordpress 3.3.1.
Site is multilanguage and links to change language looks like http://it.site.com/
After I updated to wordpress 3.3.1 ( including all plugins ans qtranslate ) links to change language looks like
http://it.site.com/ but clicking on them browser does not found pages and shows error:
"Firefox can't find the server at it.site.com."

It seems that in wordpress 3.0.0 somewhere in core of source code changes were made, which were lost during update.
Tell me, please, in which direction to search? I do do not know how domains works and where to search in code of wordpress 3.0.0.

In settings of qtranslate for “URL Modification Mode” is set “Use Pre-Domain Mode (uses http://en.yoursite.com)”