Jarmo, until now, no problems on Kerio being disable, on contrary, I can't stop the service whatever I try.
Anyway, other troubles with Kerio GUI I have a lot. Icon in system tray runs two processes (one by the System account and other by the user account, plus the Service at System account). On automatic logon, I always get the error "Couldn't reach the Service"... some seconds, the message disapears by itself, more seconds and the icon appears.
Sometimes, opening the GUI and you receive a 'monitor' freeze... all messed.