Bad normal errors

[DRedshot]

I don't really have any idea about how to solve it, apart from having a look at the normals in blender before exporting, or maybe try 'remove doubles' by highlighting the mesh and pressing 'W' (i think)
from the error it says 'length is not 1'. Maybe someone else can clear that up!

as for performance issues

Length is not 1. Will not cache file!

if it won't cache the file, wouldn't it increase loading times, and create a lag if the entity is spawned via scripts!

EDIT: If the model is a simple shape, and you find that some of the normals are facing the wrong way (i doubt this as you'd notice it straight away) you should be able to 'converge normals' or something similar in blender, then reverse the normals. this will not work for anything with faces facing inwards. But there might be a more intuitive way to make the normals point outwards, without having to do them individually