Some time cockpit beta users reported problems when viewing projects or timesheets in the administration module. The following exception occured when they tried to open a list of projects or timesheets:
Object reference not set to an instance of an object.
at System.Windows.Automation.Peers.AutomationPeer.UpdateChildrenInternal(Int32 invalidateLimit)
Finally we found out that this exception was caused by a windows service named "Tablet PC Input Service" and it is unique to entities that contain date and time fields. Stopping this service solves the problem.
Find more information under http://connect.microsoft.com/VisualStudio/feedback/details/316681/nullreferenceexception-in-system-windows-automation-peers-groupitemautomationpeer-getchildrencore.
To resolve this problem stop the "Tablet PC Input Service".