RDP using Windows CE 7 to Server 2008 R2

I use a Motorola device with Windows CE 07.00.2806 and try to connect to a Windows Server 2008 R2 getting the following error message:

„An authentication error has occurred (Code: 0x80090304).“

Already checked the security settings on the server, rdp connections should have the right permissions. also tried different logins with / without domain and different users, all of them had admin priviledges on the server --> no success so far.

What am I missing?

I've read about a possible update fix on this site (FIX: "0x80090304" authentication error), but couldn't figure out how to update a windows ce device. Could this be the solution and how can I do this?

EDIT 1

Problem was solved using a special update provided by the vendor of my device. To use the mentioned update from the KB article from Microsoft you have to use the CE image builder framework from Microsoft to build complete .iso-images for CE-devices. This was unneccessary and should be avoided as almost updates are provided by the device manufacturers.