This also applies to any products running RHEL 6.2 OS.
For VNC server to work, you must be logged in to an account on the Venice server, either root or venice. If the Venice server is sitting at the user login screen the VNC server is not running and any VNC connection attempts will be refused.
The default for user root is to prompt for a connection request, default for user venice is to refuse connect without prompting. Basically VNC is turned off for user venice.
You can adjust the VNC settings from System > Preferences > Remote Desktop. Make sure the appropriate check boxes are checked in the Sharing section and in the Security section.
The above info was verified on Venice 2U running Red Hat Enterprise Linux Server release 6.2 (Santiago).