Custom Select Query Error Message

$querystr = "

SELECT wposts.*
`FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
`WHERE wposts.ID = wpostmeta.post_id
`AND wpostmeta.meta_key = ‘tag’
`AND wpostmeta.meta_value = ’email’
`AND wposts.post_status = ‘publish’
`AND wposts.post_type = ‘post’
`AND wposts.post_date < NOW()
` ORDER BY wposts.post_date DESC
`”;

`$pageposts = $wpdb->get_results($querystr, OBJECT);

the part in bold produces error:

“Fatal error: Call to a member function get_results() on a non-object in filepath.php : eval()’d code on line 11”

anyone know why?