I use some php web software that as a part of it's functionality allows you to upload MS Word documents.

This does not work for some reason.

I tried uploading an MS Word document via FTP (i used smartftp, Filezilla) and it will not let me upload files with .doc extensions. It comes back with this error:

553-Transfer failed. You are not permitted to transfer the file "test.doc".
553 *

Does anyone know why this might be?

I am chrooted correctly when i connect - the FTP user does have permission on the files folder and i have chmod the directory to 777 too.