Cannot Establish Outgoing Connection

[Vincent Ragosta]

I have a real stumper on my hands.  We routinely establish VNC
connections to our customers for remote support.  To get things rolling,
I usually establish an outgoing connection using the VNC listener.
However, for our latest client, I cannot establish an outgoing
connection!  There do not appear to be any firewalls that would be
blocking such an outbound connection.  What else should I look for?
Thanks for your help.
 
-Vincent