Well, i don't know...

Here i tested also under MoI V1.1, which only has .iges import and it worked (under BootCamp and Windows XP SP3) and also under V2, same set-up and both files work ok and finally under OSX again with V2.52, which also works fine.

So it must be something with your set-up, but better wait for Michael.

Regards
Stefan