Losing Halion sonic presets when copying between machines

I am writing music with another person and the files are backed up and moved from one machine to another and back. When they go from mine to his, he loses the Halion Sonic presets, and has to reselect the sound. The only difference is I am using 64 bit and he is using 32 bit. All other presets are fine, including Halion Sonic SE, just the Halion Sonic ones disappear.

Does anyone know how I can prevent this happening?