Norton Internet Security can be a headache when it starts acting up, something that can be common for many large security programs. Luckily, there are a few easy steps that can get the program and your computer running better again. All you'll need is a working Internet connection to fix whatever is causing Norton Internet Security to function at less that its best. You may also want to remember how you installed it, so that you can use that method for re-installation.
Run "Live Update," a built-in feature that fixes issues by updating the entire program. If your Internet connection is working, it should connect right away and potentially overwrite any files that are not working correctly.
If a virus or other malware has found a way to block the program from working, restart your computer while hitting F8 after the initial boot screen (the first screen you see with text on it). Then select Safe Mode, a stripped-down version of Windows that allows you to run NIS (or Live Update) without the virus intruding. Hopefully NIS will remove the virus and your headache will be gone.
Google "Norton Removal Tool" or go to one of the links at the bottom to download a tool that will remove every trace of Norton on your machine. From there, a clean install is guaranteed to fix whatever quirks your last install had.