We have one Exchange 2010 SP2 server (installed on a virtual server with Server 2008 R2 Enterprise installed as OS) with Outlook 2010 SP1 clients running on Windows 7 Professional 64bit. We have a Group Policy that enables the cached-mode on all Outlook clients.
A few months ago we installed this Exchange server, and created a public folder with a calendar in it. This all works fine. We can access our public calendar through Outlook and OWA.
Since a few weeks, a strange problem occurs: every now and then (this seems usually a problem in the early morning), we can't save new items in Outlook to our public calendar.
We can still move excisting items to a new date+time and delete and edit them. When using OWA, everything works fine.
When we attempt to create a new calendar-item, the Windows 7 event viewer shows an error with ID 25: "Could not save item. The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.". The Exchange server shows nothing at that moment in the event viewer.
Every day the issue simply disappears after a few hours. I´ve noticed that sometimes restarting the Exchange Information Store (temporarily) solves the issue for that day. However, some days we are unlucky and simply have to wait.
I´m not sure if it´s related, but there is an event in the Windows 7 event viewer around the time the issue disappeared today: ID 27: "OAB Download Succeeded.".
Just to be sure I´m not forgetting any information, I attached some screenshots of the Exchange Management Console.
Any help is greatly appreciated.