As stevot mentions, the users are likely disabled or deleted in/from the AD.
Being new, you may find it easier to work with the standard graphical view and then navigate through there as you would in any other directory.
Go to the Job Setup tab, right click, select Properties.
On the left there are options, select the one called "Selections"
Expand C: and navigate to the 'Newgrove Tech' directory and uncheck it. If this does exist and needs to be backed up, make sure it is not hidden.
Then expand 'Microsoft Exchange Mailboxes' and uncheck the users causing the problem.
Check in the AD to see if they are still there, if not then they can be purged from exchange as suggested, or left - as long as they are not included in the Veritas selections your backups won't fail.
If you notice the job will still have backed up like 99.99% of your data, dispite being marked as failed, so in that respect you don't need to worry.
Hope this helps
Systems Administrator
BSc Network Computing, CCNA. Both in training!
