Bertil,
there is some bug with the current formZ plug-in and material settings specified in formZ. I don't know exactly what is going on but many material settings specified in formZ get "toned down" in the mxs export.
Open your mxs in Studio and check your materials settings. It is quite likely that your 6000W formZ emitter became a 40W emitter... This kind of thing is happening to Nd and roughness values and some more as well.
The best workaround is: use mxm materials. They don't get mixed up during export. Try the lamp presets in your materials database or simply create your own.
You should also check your scale: open the mxs in Studio and measure your objects with the viewport grid or select an object and check the data displayed in the 3d viewport top left corner.
You also may read this:
http://www.maxwellrender.com/forum/view ... hp?t=17446
Good luck
S