Strange popup in Outlook

I have a client who is using Outlook 2003 connected to two email accounts, one to a local Win2k3 server running Exchange 2003 and another to an external POP3 account.  When composing an new email when you click in the body on the email to start writing the message she gets a popup with what looks like Chinese characters and an OK button.  This pops up three or four times before going away and allowing normal use of Outlook.

Link to picture of "error:"  http://i45.photobucket.com/albums/f86/Dogfacedgod/ComMortError.jpg

I have run anti-spyware and antivirus scan without finding anything.  I'm suspecting a corrupted email but any internet searches are all about region settings and character sets.

Thanks in advance.