User name and password dialog box keeps poping up

I am connected to an exchange server. I can send and receive emails but the user name and dialog box will not accept OK. It appears as though it thinks I have the wrong user name and/or password but the mail and calendar information is flowing fine.

Hi, can you please try to update your eM Client to this release and check if the issue persists, http://www.emclient.com/dist/v6.0.22065/setup.msi ?

Thank you,
Paul