Fatal error: Call to undefined function job_search_form() in /sites/all/modules/erp/erp_job/erp_job.module

Fatal error: Call to undefined function job_search_form() in /sites/all/modules/erp/erp_job/erp_job.module on line 108

Thank line 108 says: $block['content'] = job_search_form();

This bug breaks the whole drupal site. It is a clean installation on drupal 6.20

any suggestions?