WordPress Error

Sore gan, saya ada masalah sama web yg pakai wordpress 3.5. masalah bisa kalian lihat saat membuka web 89fashions.com, ada pesan wrning dibagian atas. dan kalau masuk di halaman admin mucul pesan berikut:

‘Warning: Missing argument 2 for wpdb::prepare(), called in /home/fashion1/public_html/wp-content/plugins/wp-e-commerce-user-roles-and-purchase-history/purchase_history.php on line 54 and defined in /home/fashion1/public_html/wp-includes/wp-db.php on line 990

Warning: Cannot modify header information – headers already sent by (output started at /home/fashion1/public_html/wp-includes/wp-db.php:990) in /home/fashion1/public_html/wp-includes/option.php on line 568

Warning: Cannot modify header information – headers already sent by (output started at /home/fashion1/public_html/wp-includes/wp-db.php:990) in /home/fashion1/public_html/wp-includes/option.php on line 569′

ada solusinya gan?