Lately we have seen more and more of this phenomenon that seems to have been described earlier but I cannot find any clear solution anywhere.
ZAA is 11.2.3.24691 MU1 or 11.2.4.3271. Happens to ws that are known to have been working ok. ZAA properties goes almost blank, except Agent status show correct IP-address, Device state Managed. Configuration location says Default location, should be something else. Server properties Unavailable, Closest servers no available, no policies, no bundles.
zac ref "completes" in half a second but nothing happens. If device still has the IP-address that was known to ZEN it shows up green, otherwise "Unable to connect...".
Wireshark shows little communication with ZEN-servers and only when ws uses same IP-address as is known to ZEN. A refresh produces no communication.

Here's whats in zmd-messages.log after a couple of refreshes:
[DEBUG] [03/12/2014 08:12:34.048] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [Before call to ParseArgs] [] []
[DEBUG] [03/12/2014 08:12:34.064] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [Before call to ProcessCommand] [] []
[DEBUG] [03/12/2014 08:12:34.064] [1428] [ZenworksWindowsService] [30] [] [ZMD] [] [Processing Command for handler cache-clear] [] []
[DEBUG] [03/12/2014 08:12:34.126] [1428] [ZenworksWindowsService] [30] [] [ZMD] [] [Finished Processing Command for handler cache-clear. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:34.126] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to ProcessCommand. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:34.126] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to ParseArgs. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:34.126] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to StopDisplaySpinner()] [] []
[DEBUG] [03/12/2014 08:12:39.586] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [Before call to ParseArgs] [] []
[DEBUG] [03/12/2014 08:12:39.586] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [Before call to ProcessCommand] [] []
[DEBUG] [03/12/2014 08:12:39.586] [1428] [ZenworksWindowsService] [30] [] [ZMD] [] [Processing Command for handler refresh] [] []
[DEBUG] [03/12/2014 08:12:39.648] [1428] [ZenworksWindowsService] [30] [] [ZMD] [] [ResendLocationUpdate : -1] [] []
[DEBUG] [03/12/2014 08:12:39.726] [1428] [ZenworksWindowsService] [30] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []
[DEBUG] [03/12/2014 08:12:40.179] [1428] [ZenworksWindowsService] [30] [] [ZMD] [] [Finished Processing Command for handler refresh. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:40.179] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to ProcessCommand. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:40.179] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to ParseArgs. Result = SUCCESS] [] []
[DEBUG] [03/12/2014 08:12:40.179] [1428] [ZenworksWindowsService] [30] [] [CLM] [] [After call to StopDisplaySpinner()] [] []
[DEBUG] [03/12/2014 08:12:48.682] [1428] [ZenworksWindowsService] [33] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []
[DEBUG] [03/12/2014 08:11:00.435] [1428] [ZenworksWindowsService] [6] [] [ZenCache] [] [SqliteConnection:Setting for Asynchronous IO operation to sqlite DB read from registry is null so setting it to default to true] [] []
[DEBUG] [03/12/2014 08:11:17.117] [3192] [ZenUserDaemon] [1] [] [ZenCache] [] [SqliteConnection:Setting for Asynchronous IO operation to sqlite DB read from registry is null so setting it to default to true] [] []
[DEBUG] [03/12/2014 08:11:21.362] [3288] [explorer] [1] [] [ZenCache] [] [SqliteConnection:Setting for Asynchronous IO operation to sqlite DB read from registry is null so setting it to default to true] [] []
[DEBUG] [03/12/2014 08:34:23.928] [1428] [ZenworksWindowsService] [10] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []
[DEBUG] [03/12/2014 08:34:29.511] [1428] [ZenworksWindowsService] [52] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []
[DEBUG] [03/12/2014 08:35:04.998] [1428] [ZenworksWindowsService] [34] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []
[DEBUG] [03/12/2014 08:36:50.438] [1428] [ZenworksWindowsService] [29] [] [Settings Module] [] [Settings could not be refreshed on the device. Service Manager returned null on a call to enumerate services.] [] []

I sort of have the impression that ZAA actually is working (the services are running) but something else blocks the connection. However, Windows fw is closed and no av software is present.

Uninstall - reinstall of ZAA normally solves the problem, but this is not very practical and the situation can appear anytime on basically any ws, after which the ws remains in this state. The situation is particularly annoying on desktops with DLU, where the ws is practically useless in this state.