I AM REPLACING A LUTRON DIMMER SWITCH AND HAVE i THINK MADE ALL THE RIGHT CI=CONNECTIONS - COULD A FAULTY GROUNDING BE THE PROBLEM?

Grounding will not effect the issue.

If you are not able to get any light out of the dimmer whatsoever, then chances are that either the product wasn't wired correctly, or (and don't think I'm trying to be a **** about this, this was actually the answer on more than one occassion), the person using it didn't realize that you turn the dimmer on by pushing the knob in.

As a general rule, grounding will not affect operation of dimmer.
Type of dimmer, type of switch being replaced, type of load, and how you connect wires will affect dimmer.

Here is Lutron dimmer switch page
http://www.lutron.com/Products/StandAloneControls/Dimmers-Switches/Pages/DimmersSwitches.aspx

What is the load? Are you wiring dimmer to a ballast? Or fan? Or incandescent lights? Or florescent lights?
Are you replacing a 2-way or 3-way switch?
What color are your dimmer wires?
How many wires were connected to switch?
Can you re-install the switch, and know where each wire went?
Did you replace a light with a fan, and then want the dimmer to slow the fan? Not every dimmer will work with a fan, or florescent lights.
Dimmers cannot dim LED lights.

If I know what type switch you are replacing, and the type of load you want to control, and the specific dimmer you have, I can answer the question.