Tight VNC 1.2.9

I’am having an issue with one of 5 servers it seams that when the server is in log out mode it seems that I can not remote in on 1 out of the five using tight vnc
they are all running the same version with the same settings but the one is giving me a problem when I try to log in while it is logged out it states that their is an authentication error but if I log on to the server and then go back to log on remotly it gets on fine
thanks for your help