Error in backup that causes backup process to stop

I have files that are encrypted and cause an error in backup thus stop the backup process.  When I excluded them from the backup set they are not excluded and stop the process once again.  When I put a check mark in the excluded box for the file, I then select exclude files and then a screen pops up and asks if I am sure I want to exclude these files and I hit yes.  Any help would be appreciated.

[Edit: Clarified subject]

The best way I found to correct the described problem is to go to your actual Drive/directory/folder/file and hit your opposite mouse key, select your Norton product, select Exclude from Backup, then select OK.  There must be a glitch in Norton's backup program which unchecks the files we select  It did work for me the first time I create a new backup set but not in future backups, always the Error message.  Hope this helps.