Outlook 2007: Cosmetic Glitches While Editing Messages
After installing the KB969907 for Microsoft Office Outlook 2007, you may see cosmetic glitches while editing messages, such as repeated lines, or lines disappearing when removing other lines. This seems most prevalent when replying to an existing message and inserting a signature.
Paging down the message, and then paging up, will refresh the display of the message. If not, close the message, and allow it to save, then re-open the message.
As of July 2010, this seems to have been fixed in one of the Office 2007 updates (not necessarily an Outlook 2007 update per se). Ensure your system is fully updated.