RealVNC will not accept connections with windows authentication.
Posted by CDaze on April 28th, 2010
Not much to go wrong during the install of RealVNC that would present this problem. This can happen even after VNC is working fine with windows authentication. One day it works but the next day you are prompted with an error message with no access check logs. If you change the authentication option to RealVNC password it connects with no problems. The problem is not with RealVNC, not exactly anyway. Your windows event logs are full and not being cleaned out. Chances are you have a app that is filling up your event log every few minutes. If you can’t stop the errors from filling up your log, then increase the size and elect to have it over write when full. Probably not a setting recommended by your system admin but chances are you never check your event logs anyway. Clean out your event log and everything works again.
Event Logs can be accessed through the Control Panel. Administrator Tools is the default location, look for Event Viewer. Click here MS KB308427 for more details.