ActiveSyncDevices can't create container

Hello Community,

In our Company we have a Windows Exchange Server 2010 SP3 and following Problem:

Some Devices can syncronize without any Problems and the Exchanges Server can create the ActiveSyncDevices-Container without any Problem.
But some Users can't syncronize with the Exchange Server and the Server can't create the Devices-Container.
The Users have the same permissions as the other Users wich got no Problem.

I tried the Solutions with giving the users the rights for Exchange Server to modify permissions and also every user got the permissions to create/delete msExchActiveSync-Objects.

Can anyone help me out?

Thanks.