Printing in Outlook moves message to SPAM folder

Starting this past Tuesday, whenever I try to Print a message in Outlook 2003 it modifies the subject by adding "[SPAM]" to the beginning and then moves the message to the "SPAM" folder (I never had a "SPAM" folder before as far as I know - when I discovered it because of this problem the only messages in it were from the first message that I thought was deleted).

This happens only when printing the message from the message pane (whether previewing the message or not). If I open the message so that it is in it's own window, or if I do a Print Preview (which you can't for html messages) it behaves properly.

This happens whether I use the menu File > Print, or the keyboard shortcut Ctrl + P. It happens before the message is actually printed. When the Print Dialog is up you can see that the message is no longer in the Inbox. Even if you cancel the Print job it's still gone. If you continue by trying to Print, it Prints the next message that was selected after the message you're trying to print was moved.

I have made no changes in the last couple of weeks, and since I am the owner of this small company where I am also the sysadmin I am very sure that no one else made any system wide or workstation specific changes. The most recent change I made was to switch from McAffee to Panda anti-virus, which was more than a week before this started happening.

Thankfully I discovered that the messages weren't actually being deleted, and have figured out a way around it, but it is annoying to have to worry about it, and I have to wonder if something is quite wrong.