Open Shared mailbox in Outlook 2010

Hello,

I've made a Shared Mailbox in the OWA.

When i add this Mailbox to my OWA it works great!

When i open Outlook 2010 everything works fine.

I can see the shared mailbox i've added in the OWA but can't fold it open.

It keeps telling "The login attempt on microsoft exchange failed" (translated from Dutch)

How can i open the shared mailbox in Microsoft Outlook 2010.

Thanks!