Maybe this:
http://support.microsoft.com/kb/827742

NickHK

"Mad Scientist Jr" wrote in message
ups.com...
Has anyone tried to add a RichTextBox to an Excel form and gotten an
error "The subject was not trusted for the specified action" ?

In Excel 2003 click Tools Additional Controls and put a check next
to Microsoft Rich Textbox Control, version 6.0 and click OK. The
RichTextBox will now appear on the toolbar. Try dragging it onto a
form and that error pops up. Strange...