You can found many articles about this issue:

http://social.technet.microsoft.com/Forums/en/sharepointadmin/thread/d782e431-1034-48a6-9d57-df87dc51f0b6
http://www.bronios.com/index.php/2008/07/10/moss-people-picker-cannot-search-ad-users-from-other-domains/
http://blogs.msdn.com/b/jingmeili/archive/2007/02/26/people-picker-in-moss-2007-can-t-find-people-in-non-default-domains.aspx

http://technet.microsoft.com/en-us/library/gg602068.aspx