[support] warning: call_user_func_array() [function.call-user-func-array] error. any solution?

Dear All, i got an error warning in my drupal site. I coulnt figure it out and how the error came. The error text below: warning: call_user_func_array() [function.call-user-func-array<http://216.106.58.94/function.call-user-func-array>]: First argument is expected to be a valid callback, 'search_form' was given in .......\includes\form.inc on line 366. Whats the error and how can u solve this? I got to fix this soon. Thanks for your support in advance. With regards Crazyguru