In Windows Mail, the Sent Items and Deleted Items are invisible. How to get them back?

A few weeks ago, my husband’s computer started having this problem. When he sends an email, it doesn’t show up in Sent Items. Nothing shows up; it just says there are no items in that view. The same thing happens with the Deleted Items folder. It says there are X number of unread messages in Deleted Items, but when we click on that folder none of the messages show up. However, if we search for a message that we know is in the Sent or Deleted folders, it shows up in the search results. So we know the emails are there, we just can’t see them!

We have Windows Vista Home Premium and Windows Mail Version 6.0. I’ve tried looking it up online, and all I can find is a suggestion to uninstall security programs to see if that makes the email work properly. I tried that, but no luck. We have Constant Guard Protection through Comcast Xfinity, which includes the Norton Security Suite.

Email settings are set to automatically put sent emails in the Sent Items folder. Both folders are set to view all messages. We’ve had this computer for a couple of years, but the problem only just popped up. Also, we’ve installed the available updates plus anything else I could think of.

Has anyone else had this problem or does anyone know how to fix it? Since this is the computer my husband uses for his business, not being able to access those folders is a real problem. Thanks in advance!