Running ZCM11 SP1. I'm in trouble with one workstation that cannot be remote controlled. Remote Control attempts fail with the dreaded "Rights authentication failed" message, which is complemented by another sentence "The managed device could not contact the Zenworks server"

I've tried the usual stuff:
verify workstation and server time are in sync - check OK.
verify that forward and reverse DNS lookups work from client to server and server to client - check OK
verify that correct certificate is in registry - check OK
zac cc
zac unr / zac reg
disable antivirus
disable firewall
reboot

None of these helped. When I uninstall the agent and reinstall it, remote control works initially, but starts failing again after short time (sometimes by next day, sometimes as soon as after one hour). I've uninstalled and reinstalled the agent several times, but I really need to find a more permanent solution.

When I look at zmd-messages.log on the workstation, I'm seeing these "interesting" messages:

Code:
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [FindFirstContent()] [] [] 
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [   ] [] [] 
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [ ] [] [] 
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [   Found host thor.tlvsise status: Good] [] [] 
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [   Found location https://192.168.1.47/ status: Bad] [] [] 
 [DEBUG] [04/16/2012 14:42:53.694] [1544] [ZenworksWindowsService] [17] [] [ConnectMan] [] [   Skipping IP location: https://192.168.1.47/, status: Bad] [] []
I compared that with zmd-messages on another workstation which doesn't have the problem, and there are no "status: Bad" messages:

Code:
[DEBUG] [04/16/2012 14:54:07.140] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [FindFirstContent()] [] [] 
 [DEBUG] [04/16/2012 14:54:07.140] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [   ] [] [] 
 [DEBUG] [04/16/2012 14:54:07.140] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [ ] [] [] 
 [DEBUG] [04/16/2012 14:54:07.140] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [   Found host thor.tlvsise status: Good] [] [] 
 [DEBUG] [04/16/2012 14:54:07.156] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [   Found location https://192.168.1.47/ status: Good] [] [] 
 [DEBUG] [04/16/2012 14:54:07.156] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [   Using location https://192.168.1.47/ status: Good] [] [] 
 [DEBUG] [04/16/2012 14:54:07.156] [1144] [ZenworksWindowsService] [14] [] [ConnectMan] [] [FindFirstContent() returning https://192.168.1.47/] [] []
I have not defined any Locations at all in my Zenworks zone, and it doesn't seem to bother any other workstations. What should I do to get rid of this "status: Bad" situation on my problematic workstation?