Onestepcheckout.com: Registered Customers forced to login upon checkout

[m-overlund]

Hi

Customers who are already Registered customers, are being forced to login upon checkout, when entering their email addresss.
Onestepcheckout.com says this is standard behavior and not possible to change.

However i don't have this issue on other (older Magento) installations, with OSC checkout.
Anyone had this issue or know how to fix?

It is kind of a conversion killer