After updating Unity, SkinnedMeshRenderer requires a mesh with skinning information everywhere

Hi...

I have been working on a project for many months now in Unity 3.5 and ,though hesitant, decided to update to Unity 3.5.5f3. Now many of my scenes appear jumbled. Most objects appear closer to the origin than before and black. I get the "SkinnedMeshRenderer requires a mesh with skinning information" from all my character models. I have tried re-importing all assets a few times but still the same.

Here is a screenshot of a scene now:

Any help would be much appreciated.