In CS-Cart v.4.3.5 the authors introduced major changes in all Paypal payment engines. These changes made the add-on to not forward the right amount value and the selected currency to PayPal payment page.
Our enginners developed a completely new engine that is compatible with the introduced changes. If you updated your CS-Cart to v.4.3.5 you need to update also the PayPal Express Multi-Currency add-on.
More info: PayPal Express Multi-Currency v4Share