Am having trouble with the onepage checkout on an installation of v1.9.01 . Where the response of /checkout/onepage/saveBilling is blank. Form details are being passed through but the script effectively bombs out at a key point.

The problem occurs in Mage/Checkout/Model/Type/Onepage.php

    if (($  validateRes = $  address->validate()) !== true) {         return array('error' => 1, 'message' => $  validateRes);     } 

It seems that $ address->validate() is not a valid method. If I comment that out then it errors on the next bit

$  address->implodeStreetAddress(); 

I cannot find either the validate() method in the sales-quote-address areas or the implodeStreetAddress() method anywhere. I am not sure if I have had a patchy patch (!) or am missing some understanding of these.

Oddly the site seems to be working in dev but not live. Can anyone advise?

UPDATE The implodeStreetAddress() method is in app\code\core\Mage\Customer\Model\Address\Abstract.php: