I've never used an .mx file; however, from the documentation:
"MX files cannot be exchanged between different operating systems or versions of Mathematica."
"Mathematica MX files can be created with DumpSave and read with Get."
Did you save the source files from which you did a DumpSave? If so, move the source files to v9 and DumpSave new .mx files in v9.
On Tue, Dec 11, 2012 at 2:24 AM, NBM <firstname.lastname@example.org> wrote: > Having written a lot of code on M8, I recently switched to M9 and tried to > run the code which starts by loading an .mx file written by M8, but M9 wouldn't read it saying that it was written on another machine. This is a major incompatibility issue between M8 and M9. Fortunately I kept my M8 installation, so for now, M9 is useless to me. > Please a solution. >