Normal VNC does not get you the actual screen where the physical monitor is connected, it opens a virtual screen, so you at remote are not seeing the screen the customer is looking at.
x11vnc is needed to accomplish the above.
VNC to screen 0:
On Venice/SBU (RedHat RHEL 5.3), download and install x11vnc.
Should be on Jake/support/robert.
CLI is: x11vnc -forever
To autostart in RedHat 5, put "x11vnc -forever" in the Startup Programs list. It is located at System > Preferences > More Preferences > Sessions. BUT! The local screen must 1st login for this to start!
On the VNC client: use screen 3 or something close to it: vncviewer 10.10.10.27:3