outlook 2007 problem

Hi All
I have a user with outlook 2007. When he saves an email as an HTML it deletes the email from his inbox. This does not happen every time. When he demonstrated the problem to me he saved an email by doing a save as to a network drive. The email was saved to the drive but was also deleted from the inbox. He then did the same for another email and that one was not deleted from the inbox. He wants the emails to remain in the inbox. Any ideas?