Search module not retrieving all results ?

Hi

There seems to be a problem with the search module (perhaps the index)

When searching for a Username string, we're not getting the expected results (see attached backend and frontend screnshots here).

http://sewingtribe.com/images/tmp/search-backend.jpg
http://sewingtribe.com/images/tmp/search-frontend.jpg

I've set up your access codes for this ?

You should know that these 20,000 users where imported with a custom DB script.

The searching seems to work when we search for users that where created through the Joomla/EasySocial interface ...

Please advise
Thanks
Danny