With the eCart store order summary and store order details server behaviors it will either insert a new order or update an existing one. If the order is already in the db then you should not get an error from this server behavior.
If Linkpoint is sending this error message and you attempt to run the transaction again you will get an error like this about the order having already been processed. Do you have any custom order recording or error messaging on any of these pages?
If you are getting this error closing the browser and opening it again should clear up the problem. Please let us know if you continue to have this problem and if it is something you can reproduce with a set of steps.
I believe that Linkpoint is sending the error when a customer tries to re-submit their order and the session id (which is the order number that goes to linkpoint), does not change on their second attempt. This only happens when an order is declined by linkpoint. I do not have any custom order recording or error messages.