I ran into the same issue this past weekend.
I think the problem in my case was that Nero would not allow me to burn the .iso to a DVD, and my xbox refuses to read cd-rw. I ended up using DVD decryptor to convert it to DVD.
Now, the xbox will boot to the evox installer dash from the DVD-R, and even format the drive (thankfully) however, it does not copy the files over.
Whatever the case, to solve the problem I used xiso to extract the files from the DVD-R (not sure I had to use that program in particular to break out the files).
at the root of the disk there is a file called evox.ini if one reads through that there are several copy commands detailing which files need to be copied where on the xbox depending on the type of install. In my case a large rebuild.
copy "%SYSTEM\ALL\c\" "C:\" or something like that.
Once you have the files on your PC they can be copied to the proper directories on the xbox via FTP using the evox.ini as a template.
In the example above open the root folder\ALL\c folder, and copy the contents to the C: drive.
Everything works fine for me.