Ok, I have found something.

Basically, if I insert a Word 2003 document in my table and do the same process it works. Basically, all Word 2003 files would work. However, if I added a Word 2007 file in the general field and do the same process, the file is corrupted. So, basically, I guess the header signature has changed. However, I looked at some information on the net and it seems the header signature hadn't changed.