Live Characters and false joint rotations

[Vaquero]

Hey there!
I'm still struggling with getting third party and custom made characters to work with the Live Characters Plugin. This time, it seems the joint orientation has an unwanted effect on the animation as you can see in the attachment. In the inspector the character stands in its T-pose and looks fine.
But it can't exactly be the joint orientations, because the sample characters do have them, too.
I tried with a character I made myself and with the character you see in the picture that I downloaded from the Autodesk Character Generator.

I really need help with this, as I can't figure out what's wrong.