I have loaded Norton 360 version 3 on three

I had the same problem and apparently Norton saw fit to add a fix on their support site. Go to the Help & Support link at the upper right corner of your Norton screen. Go to Get Support. Click the Support Resources link at the lower left of the screen. In the search field type "Norton 360 Version 3.0 does not recognize the CD or DVD drive when you start Backup". It will bring up several choices for problems but the upper choice should be an exact match for what you entered. This will take you to a step-by-step solution to downloading GEAR software which when installed, resolved my issue. It did not require a restart though like the instructions indicated. Both my drives were recognized immediately. Hope you have the same success!

try to un-install the norton 360 v.3 and see if it work again. If does, then something wrong with the program, try different one.