Error after checking out

Using:
WP v3.4.2
Theme: Enfinity
Woocommerce Version 1.6.5.2
WooCommerce SagePay Direct Payment Gateway Version 0.1.1

I get the following error after checking out using a CC and sagepay direct:

{“result”:”failure”,”messages”:”
\n\t\t\t
Action failed. Please refresh the page and retry.<\/li>\n\t\t\t
Sorry, your session has expired. Return to homepage →<\/a><\/li>\n\t\t\t
First Name<\/strong> is a required field.<\/li>\n\t\t\t
Last Name<\/strong> is a required field.<\/li>\n\t\t\t
Address<\/strong> is a required field.<\/li>\n\t\t\t
Town\/City<\/strong> is a required field.<\/li>\n\t\t\t
Postcode<\/strong> is a required field.<\/li>\n\t\t\t
Country<\/strong> is a required field.<\/li>\n\t\t\t
Email Address<\/strong> is a required field.<\/li>\n\t\t\t
Phone<\/strong> is a required field.<\/li>\n\t<\/ul>”,”refresh”:”false”}

The order actually went through though and the transaction appeared as completed in the sagepay account, so I am presuming it may be to do with the plugin compatibility, but really I am clueless. Any suggestions please?

https://www.ads-software.com/extend/plugins/sagepay-direct-for-woocommerce-payment-gateway/