Are you sure you downloaded the Collada file (.dae) when you download from the 3D warehouse - as described in the 3D Models import page and the FAQ ?

Tried both models, and they both imported with no problems at all. (Btw: Flexform Piuma Cabinet has textures applied only to one side of its surfaces, so it may not render as nicely as it should - but that is more a design shortcoming than a SH3D issue).

ok