This one:
Serious problem loading model 'x', 'y' normals capped to zero
I fix it by either 2 methods depending what's wrong with it.
1. I open the model in Truespace, right hand click it to edit the mesh, then retriangulate it. The polycount should go down a bit and that seems to fix it. It's a weird way to fix it but it worked for most of them so far.
2. I have to move some near overlapping verts so that I can weld them together using 3DE. I only had to do this on the Ophion since the slice plane I used during UV Mapping caused some corruption.
For us it seems to happen a lot on models that have been converted to 3ds at some point. Looks like overlapping verts that haven't been welded correctly cause it.