ok, I asume the problem is /includes/sessions.php, because search uses sessions.
so, lets try avoid using it, and use "inline" parameters instead.
try this:
in search.php find:
$link_arg = $site_sess->url(ROOT_PATH."search.php?show_result=1");
Replace with: $link_arg = $site_sess->url(ROOT_PATH."search.php?search_keywords=$org_search_keywords&search_new_images=$search_new_images&search_user=$org_search_user&search_terms=$search_terms&cat_id=$search_cat&search_fields=$search_fields");