I'm having exactly the same problem. When I use createdocx it creates the file successfully on the server and I can download it and everything looks ok. I need to use createdocxanddowload but when I do it just puts binary information onto the screen.
I downloaded and installed the software just today, Nov 21st. All the tests and creation on the back-end work fine I just can't automatically download the files.
It happens in IE9 and Firefox 17.0.
If anybody can help I'd appreciate it.