VMware Update Manager: The session is not authenticated

Today I ran into strange issue with the VMware Update Manager 4.

Whenever I tried to enable plug-in I received following error:
There was an error connecting to the VMware vCenter Update Manager [VUM server name:443].
: Vmomi.Fault.NotAuthenticated : The session is not authenticated.

Also the C:\Users\All Users\VMware\VMware Update Manager\Logs\vmware-vum-server-log4cpp.log logged only the "Not Authenticated" error.

------------------------------------------------------
Invoking login on integrity.SessionManager:Integrity.SessionMgr session "SessionID"
Arg userName: "DOMAIN\Username"
Arg sessionId: "Session ID"
Arg locale: "en_US"
------------------------------------------------------
[2011-11-02 08:42:01:123 'Activation.trace' 3388 DEBUG] [activationValidator, 1094] Throw vim.fault.NotAuthenticated
Result:
(vim.fault.NotAuthenticated) {
dynamicType = ,
faultCause = (vmodl.MethodFault) null,
object = 'vim.Folder:group-d1',
privilegeId = "Sessions.ValidateSession",
msg = "The session is not authenticated.",
}
[2011-11-02 08:42:08:699 'JobDispatcher' 1852 DEBUG] [JobDispatcher, 391] The number of tasks: 0



The only one change which occurred since my last logon was the time change from Summer to Winter...:) 



To solve this issue you just need to restart the VUM service:

And re-enable the vCenter Plug-in: