PayPal - When Customer Cancels a sale a blank page appears.

[fearialtog]

When a customer hits the cancel and return to website link on the Paypal log in page the following url is generate but the page is blank.

https://mysite.com/index.php?option=com_virtuemart&view=pluginresponse&task=pluginUserPaymentCancel&on=79a???70&pm=3

The above url is not set anywhere in paypal settings but the one below is.
https://mysite.com/administrator/components/com_virtuemart/notify.php

Changing SEO settings has no effect.

Any help would be gratefully appreciated.

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VM 2.0
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