Weird Outlook error
 

This is a strange one I have never seen before. I have a user on Outlook
2003. On some emails when he tries to reply, it pops up an error message:

"A program still has file attachment image001.jpg open. Changes to this
document will be lost unless you save your changes to another file by
clicking the File menu in the other program, and then clicking Save As"

This does not happen on any specific type of email, and not always on the
same ones. Nothing is showing up in the Event Viewer about this either.
Please help.