Intermittent error on reading sub-folder in Outlook

With the help of my friends here on this forum, I was able to write an application to read emails from a folder, download the attachments to a windows folder, and move the email into a subfolder. It works well most of the time. However, if it runs into an error, it not only stops, but fails to work from that point on. I was running the program and encountered the error message in the first picture. I stopped the program and ran it again and got the second error message. I closed Excel, re-opened it and ran the program and got the second error message again. The only way to clear the error is to close Excel, close outlook, open outlook and open excel again.

When it fails, the program always errors on this line:

et FldrOut = olNS.Folders(MailBox).Folders("Inbox").Folders(InFolder).Folders(SubFolder)