After a quick test drive it seems Carrara doesn't like your scaling, the third leg is broken. I can probably fix this by zeroing the figure in Poser and resaving.

I wish I knew how to set up IK as that would make posing somewhat easier, it would have to be done in Poser and I'm not conversant enough with the rigging stuff there.

For those who'd like to make morphs for unwelded meshes, you can use the free Morpher available in the freebie area here.

Edit: just tested in Poser 8 and apparently IK is set up, but for some reason the figure falls apart in Carrara if I try to translate body parts.

Edit 2: Okay never mind, this is what I get for not having my coffee before testing :-] IK works with feet but not with hands, same in both Carrara and Poser.