Outlook 2003 error "The messaging Interface has returned an unknown error, if problem persists, restart outlook

We have a Windows XP pc that we upgraded from Office 2003 to Office 2007. When we experienced application compatability issues, we removed Office 2007 and reverted back to office 2003.  Now we have a printing problem in Outlook 2003. When we try to print an email message, we get the error: "The messaging Interface has returned an unknown error, if problem persists, restart outlook." Restarting outlook does not resolved the issue. I applied Office SP3 but the issue is still occuring. We have found that if we open an  email message, hit the reply button, and then try to print....printing works. But if we open the email message and try to print, we get this error.