I can't find anything wrong in this log. My guess is that it could be Norton. Boot into Safe Mode and see if you have this problem also. If not, it must be one of the Norton programs.
See if you can do the following virus scan online (if it's not too slow for this also):
If you have a fast internet connection (broadband), run an online virus scan at
TrendMicro. Just follow the instructions on the site to run the online scan. Otherwise, make sure your antivirus program has the latest definitions and run a full system scan.