Have you checked to see if the path to the encoder is correct?
To check that:

1. Open up DVD Rebuilder (DVD-RB), click options then setup.
2. Click the button to the right of the encoder your using, browse to where it's installed, select the main executable and click Open.
3. Click OK.
   note: if your using Cinema Craft Encoder (CCE) then you'll need to click on options, then CCE options then select the version of CCE your using.
4. Then click Mode and select the encoder you entered the path to previously.

If this doesn't solve your problem then you'll need to supply addition information before anyone can help further, we're no psychics you know.

Information such as software version (free or pro), your settings and any errors and what they are.