Can't change users group since upgrade?

[alexzien]

I can't change a users group (permissions) in VirtueMart 2.0.12b. I could do it before the upgrade. This is very weird. But when I change the users Joomla group also the VirtueMart group changes. But I don't want that... I have a customer who's only going to have full access to VirtueMart and not other parts of the Joomla administration. Therefor I need to be able to set the customer to the "admin" group in VirtueMart manually, like before.. How do I do that now?