Basically you need try running live update, if that doesnt fix it, try un-installing all Symantec Products, restart, and install again.
Your virus Definitions file is corrupt.
Since you cant get that page loaded, ill copy the relevant info you need from it..
Quote:Error: "Norton AntiVirus was unable to scan your computer for infections because virus definitions could not be loaded . . ." (3019,5)
Situation:
When you run a virus scan, you see the message "Norton AntiVirus was unable to scan your computer for infections because virus definitions could not be loaded. Start LiveUpdate to get latest virus definitions and scan again." In the lower-left corner of the message box, you see the numbers 3019,5.
Solution:
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Before you begin: This problem should be fixed by the latest Symantec Common Client and Norton AntiVirus program updates. To install the updates, start Norton AntiVirus, run LiveUpdate, download all available updates, and then restart the computer when prompted. For more details on how to run LiveUpdate, see the document How to run LiveUpdate.
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If the program update does not fix the problem, then this error can occur if the Norton AntiVirus virus definitions are damaged. To fix the problem, do the following in the order that they appear. If the first solution does not fix the problem, then try the second solution.
Update the virus definitions from the Symantec Web site.
Uninstall and reinstall Norton AntiVirus.
