I am getting message

Sorry your transaction wasn't recognized. Click the link to return to checkout page.

I am using SagePay and that i can replicate the mistake - It's essentially should you wait age range around the SagePay finish then process payment - and also the SessionID is missing.

Can anybody help?

Regards

Shane

Solved it this finish:

http://keyzo.co.uk/blog/wordpress-wp-ecommerce-and-sagepay/

Hope it will help someone else.