This is a common problem occure due to Virus guard Problem. Most of the time this happen with Norton Internet Security software. Try to uninstall virus guard and reinstall a virus guard properly again. Hope This is working. I have lot of experience with this error with my life and 100% of this problem comming due to error on Virus guard specially Norton Internet security.
Use Linux. No Virus attacked. No Virus Guard need. No Virus Guard classes.