L recently purchased a Lutron dimmer to replace an older dimmer. Out of the box is a red white and black wire.. no ground, and on the dimmer itself is a black wire and 2 red wires ( one with a white spiral stripe ) I've tried every combination without connecting black to white, and now I cannot turn the light on with the switch. And if the switch is in the on position I cannot turn the light on with the dimmer. How can I right this wrong?

What is the model number of the Lutron dimmer you have?

Its CTCL-153P (skylark contour)

According to the installation manual, the black of the dimmer needs to connecto the common wire of the 3 way circuit, leaving the two travelers in the box to connecto the remaining red and red/white wires.

What you need to do is confirm which wire in the box is the common.

http://www.lutron.com/TechnicalDocumentLibrary/032365.pdf

Thank you for the info I reversed the application took the switch out and in its place I installed the dimmer and where the dimmer was went the switch. The white wire in the box with the switch was common. Go figure!

Connecting a white wire to a hot will always make you think twice.

The red with white gets capped for single pole use.
They do this so for single pole operation it will be more natural/normal.
In three way application, it is always swapping.