Can't open programs, files or use Internet after full system scan

I have Norton Antivirus 2012 that I purchased  in December. I performed a full system scan, and now I can't open almost any programs and files, or  have an Internet access. I tried to do a system restore in safe mode but  was not able to do it. I don't know what to do; I never had such problems with my computer until I installed Norton. ...Please, help!!!!