To act on behalf of customer in additional store

[hani]

Hi all

I have Abantecart 1.4.2.1 installed and a multistore and i tried to act on behalf of a customer in the second store and i get this message:
To act on behalf of customer in additional store you should to login into another store's admin side. Continue?

When i try to login using the admin of the second store i get a message INVALID TOKEN / SESSION

Any help??