VM users seem to be out of sync with Joomla users

[GooRu]

Hi...

When a user makes a purchase on site they must create themselves a user account to do so. When they do and visit the cart, they will see someone else's details and those details are of a Joomla user previously created. Clearly the users in VM and Joomla are out of sync!

How do I deal with this?

VM 2.0.26
J! 2.5