Do you have any other antivirus or firewall products installed? This is really important, as other security products can block the updates.

I am a bit confused here. What is the Norton product you have? Is this Norton 360 or Norton 2011 product?

If you do not have any other security product, please download and run the Norton Removal Tool, and then reinstall the Norton product. You can download the Norton Removal Tool, depending on your Norton product and version from:

http://www.symantec.com/symnrt

After you run the Norton Removal Tool and restart the computer, you will receive the instruction to download your Norton product. Download it, install it, and then run LiveUpdate.