can someone help me with this error message - blank page add-to-cart

[romeo2die]

Hi there,

My condition right now:
1) I recently upgraded my joomla from 2.5.11 to 2.5.28, and also I upgraded my VM from 2.0 to 3.0.9.
2) I'm also trying to install 3rd party payment system (for local currency payment)

After I installed the payment system, whenever I click add-to-cart button, it will show only blank white page (I've tried following all the steps  posted on the forum but I'm still stuck here).  After setting up the error msg to maximum, I got this message when I click add-to-cart button:

Fatal error: Call to undefined method VirtueMartCart::prepareCartViewData() in /home/klikmcc/public_html/plugins/system/vponepagecheckout/cart/cartview.html.php on line 1118


After checking that line, here's what shown in that specific line (1118):
$cart->prepareCartViewData();

I also checked the error log and the last one I got is this:

ERROR vmError: VmTable #__virtuemart_paymentmethods_en_gb Check not passed. Neither slug nor obligatory value at payment_name for auto slug creation is given 0


Can someone help me with this problem? much appreciated!

Thanks in Advance

[jenkinhill]

Looks like you need to update your VirtuePlanet One Page Checkout, an update was published in June, 2015.

[Studio 42]

First try with the protostar template(i doubt this solve your problem).
Check for onepage checkout update for Virtuemart 3 and change your current template with one from OPC default templates.
Contact OPC support.

[romeo2die]

Thanks everyone for the reply, much appreciated!

So can I just simply disable or uninstall 1-page plugin to solve this problem?

[GJC Web Design]

Yes ....  disable first to see if this is the problem .. as 42 says -- try the std. templates as well