This has come up before and I've followed this answer but no joy.
I'm trying to upload a .docx file to my CI app but it's giving me
The filetype you are attempting to upload is not allowed.
Now, when I vardump the mimetype of the received file by changing line 199 of system/libraries/upload.php to
$this->_file_mime_type($_FILES[$field]); die(var_dump($this->file_type));
I get
application/vnd.openxmlformats-officedocument.wordprocessingml.document; charset=binary
...and that IS listed in my application/config/mimes.php file as an acceptable mime for docx.
This being the case, what else could be wrong?