Need to access VNC on CentOS asap - @ dead end - please help

I just created a CentOS 6 32 deployment on my Linode 512 and followed the instructions on CentOS to activate VNC.

I have tried to access it via an VNC client on my laptop, but get a "Connection Failed" notice from the client app. So, it doesn't appear to be a authentication problem or anything like that and the Cent OS command line indicates the VNC is running.

Is there something I'm missing? Does Linode block this kind of access for security reasons, and require me set up a VPN or something? Is it not a Linode thing but a Linux or CentOS thing? Is there more I need to install?

I need to get access via VPN asap to do an emergency migration, so I' hoping someone can help me soon! :)

Thanks!