Ypnos,
I think only Pavol can really help you with the installation problem. Try e-mailing him: (pavol@dunako.com).
First check these:
Do you have MaxwellExport.dll 1.0.3.7 in your SketchUp Exporters folder?
Do you have MaxwellExport.rb in your SketchUp Plugins folder?
(I don’t know if those two are the only ones needed).
Sheik
ps. Is OS X installing well and working?