I am running Joomla 3.4.8 and VM 3.0.12 and I have customers telling me they see an "Error Updating Cart" when they agree to our terms and click on Checkout Now. Our payment method is Authorize.net and it worked as of 8pm PST last 2/4/2016. Any ideas as to what causes this? We seem to be unable to process orders at this time which is bad news.
In a similar case (but related to PayPal) users seem to have had a problem with the Ajax for OPC setting in VM. Might be worth to check this until somebody has a better idea.
http://forum.virtuemart.net/index.php?topic=132491.0
That seems to have fixed it!
Strange that everything has been working swimmingly until last night with all the current settings. :o