Marketpress suddenly calculates all sums wrong

Marketpress calculates all order totals wrong.
Can you please help and tell me how I can get Marketpress to calculate correctly again?

Here is a screenshot from an individual order:
https://www.dropbox.com/s/cznvfqlyampdart/Screenshot%202015-12-14%2012.06.27.png?dl=0

You can see that the order total is completely off.

thanks for your help,
boris

PS: I have granted you support access to the site to look at the problem first hand. Please note though, that the orders you see are live orders not test orders, please do not alter or delete them.