This is for the desktop client. Since the upgrade yesterday, Zimbra client will not sync. Here is the error message:

Code:
Failure communicating with remote server. Please try again later.  (debug info)

Debug message: resource unreachable: Internal Server Error

Exception:

com.zimbra.common.service.ServiceException: system failure: InitialSync.syncCalendarItem
ExceptionId:mid=2:1235650892203:8bb8264a14e5dac7
Code:service.FAILURE
	at com.zimbra.common.service.ServiceException.FAILURE(ServiceException.java:253)
	at com.zimbra.cs.mailbox.SyncExceptionHandler.checkRecoverableException(SyncExceptionHandler.java:40)
	at com.zimbra.cs.mailbox.InitialSync.syncCalendarItem(InitialSync.java:681)
	at com.zimbra.cs.mailbox.DeltaSync.deltaSync(DeltaSync.java:237)
	at com.zimbra.cs.mailbox.DeltaSync.sync(DeltaSync.java:92)
	at com.zimbra.cs.mailbox.DeltaSync.sync(DeltaSync.java:76)
	at com.zimbra.cs.mailbox.MailboxSync.sync(MailboxSync.java:184)
	at com.zimbra.cs.mailbox.OfflineMailbox.sync(OfflineMailbox.java:140)
	at com.zimbra.cs.mailbox.OfflineMailbox.syncOnTimer(OfflineMailbox.java:121)
	at com.zimbra.cs.mailbox.DesktopMailbox$1.run(DesktopMailbox.java:436)
	at java.util.TimerThread.mainLoop(Unknown Source)
	at java.util.TimerThread.run(Unknown Source)
Caused by: com.zimbra.common.service.ServiceException: resource unreachable: Internal Server Error
ExceptionId:mid=2:1235650892203:8bb8264a14e5dac7
Code:service.RESOURCE_UNREACHABLE
	at com.zimbra.common.service.ServiceException.RESOURCE_UNREACHABLE(ServiceException.java:275)
	at com.zimbra.cs.service.UserServlet.doHttpOp(UserServlet.java:1447)
	at com.zimbra.cs.service.UserServlet.getRemoteResource(UserServlet.java:1281)
	at com.zimbra.cs.service.UserServlet.getRemoteResource(UserServlet.java:1274)
	at com.zimbra.cs.service.UserServlet.getRemoteContent(UserServlet.java:1248)
	at com.zimbra.cs.mailbox.InitialSync$RemoteInviteMimeLocator.getInviteMime(InitialSync.java:115)
	at com.zimbra.cs.mailbox.InitialSync.makeSetCalRequest(InitialSync.java:775)
	at com.zimbra.cs.mailbox.InitialSync.syncCalendarItem(InitialSync.java:669)
	... 9 more

If issue persists please post description and debug information here.