One of my users has run in to a problem with the Desktop Client. When she tries to remove an attendee from an appointment that she is the organizer of while using the Desktop Client, she receives an error indicating the Client is in Offline mode. The icon next to 'New Calendar' indicates she is indeed online.

If she loads up the web client, she can remove the attendee just fine. This is using ZDC1 and Zimbra NE 5.

Any known issues or fixes for this?