Problems configuring humanoid avatar. Muscles settings are disabled

Good day!

I'm using Unity 4.2.2

After importing rigged character (exported from 3dMax in fbx format) and fully correcting bones mapping for Body, Head & both Hands (they all show up as green) the avatar is still not configured properly for some reason and I'm unable to figure why.

My Character is in T-Pose and all green: Pic

Mapping is all green & for all other parts of the body too: PIc

Muscles tab is disabled, nothing works there: pic Pic

Rig configuration looks like this: Pic

There are no errors in console or any other hints regarding what's wrong :(

Please help!