I am under Windows 7 x64
There is no non-english characters and it is not working with any of my stl files.
Stl are not so big, and as I said it is not working with any of my files.
And finally, Daid, I have done that, my stl files need to be resized before printed.
Maybe I have to say that we are using dual extrusion too. The problem appeared when I uploaded two stl to make a dual extrusion (it worked before for the same joining), tried to save it as amf and to reload it but no way to save it as gcode.