[Zope] ExtFile - wrong file extension and content_type

All, I am working on a project using ExtFile. Lately, when uploading MS Word files, they get uploaded to the file system as .exe files (eg. test.doc becomes test.exe) and the content_type is set to application/octet-stream instead of application/msword. Sometimes the content_tpye is correct but the file extension is still set to .exe. Does anyone know what could be causing this? Is there a config setting in ExtFile that's doing this? Any ideas would be much appreciated. Thanks, Tom