in search-unleashed/modules/nextgen_gallery.php lies the reference to the nextgen searchnggallerytags hook.

// Action calls for all functions
add_filter ('the_content', 'searchnggallerytags');
add_filter ('the_excerpt', 'searchnggallerytags');

simple workaround until the author fixes the plugin dependencies is to comment the lines.

// Action calls for all functions
//add_filter ('the_content', 'searchnggallerytags');
//add_filter ('the_excerpt', 'searchnggallerytags');
照上面的改完后， 搜索就正常了