[CentOS] Remote Desktop on CentOS 5.3

Does anyone have remote desktop connectivity working in CentOS 5.3?   
I'm using the Gnome desktop and have configured the Remote Deskop  
Preferences to "Allow other users to view your desktop" and "Allow  
other users to control your desktop".  The configuration dialog box  
says that "Users can view your desktop using this command: vncviewer  
HOSTNAME.domain.com:0".  However, when I try to connect to it from  
another host, I always get a "Connection reset by peer" error  
message.  I've tried various different clients an operation systems,  
and I get the same result.  I disabled the firewall completely for  
this test (service iptables stop) so I know it's not a firewall  
issue.  Then again, I don't see a vncserver process running either,  
so that may be the issue.  This was working on CentOS 5.2.

What do I need to do to access my existing desktop on my CentOS 5.3  
system remotely?  I don't need to use VNC, but I do want to access  
the existing session and not a separate desktop (i.e., by starting a  
vncserver process).

Thanks,
Alfred