To get you the best advice, would you give us some more information about your system:
What version of Windows are you using including Service Packs and whether 32 bit or 64 bit as well as the Name and Version ID of the Norton product that you are using -- Help or Support / About is where that is, in the format of nn.nn.nn.nnn where n is a number.
If you have the COMCAST version of Norton 360 / Security Suite and not the normal retail version please be sure to tell us.
If you get any error messages please give the exact wording of them as well as any other background that could be helpful.
Please also say what internet browser you are using -- name and version number ...
When it finally reboots do you get any error messages (and did you get any on the blue screen where they are often in weird codes with lots of 000's and letters etc) If so please tell us exactly what they say since then we can look them up.
When if finally boots up does it then behave normally every time you restart.
We can't see or touch your machine so we need all the help you can give ....