can't submit order, Fatal error ps_authorize.php on line 423

[topmanx]

Hi, i need help from you guys.
I can't submit order with authorize.net. When i submit my orders, i get this error message:

Fatal error: Call to a member function f() on a non-object in /var/www/tenren1/administrator/components/com_virtuemart/classes/payment/ps_authorize.php on line 423

I have right API login and transaction key. 

[topmanx]

update:

I just checked and the transaction actually did went thru authorize.net. But the problem is whenever i submit orders, i do receive this error message, and the order doesn't show up in virtuemart's order list.

[Joseph Kwan]

what version are you using? try replacing that problem file again from the vm download.