Outlook 2013 - Disconnect every 10-20 min.

Hi,

Situation:

• Two Exchange 2013 CU1 Mailbox Role servers (DAG cluster) Windows 2012
• Two Exchange 2013 CU1 Client Access Servers - Windows 2012
• Workstation Office 2013 - Windows 2012

Problem:

Every 10-20 min Outlook disconnects.
When I look in the eventviewer the RpcHttp Application is shutting down.
Afther 1 or 2 minutes everything works again. 

A couple of users don't use cache mode in Outlook 2013 so they cant work the outlook when its disconnected.

Ather a search on the forum someone posted to add:HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\MinimumConnectionTimeout (value 120).

But it still disconnects som times. 
Does anyone has the same problem and know how to fix it.