this is what i found on steam.
jforthdesign
It's all down to the latest DirectX exporter that comes bundled with Blender. I don't know what broke it or what was changed, but, the exporter in 2.69 works perfectly. You can have more than one version installed at the same time. I use 2.69 for my game work and 2.71 for my renders.
Inverting the normals on export doesn't always have the correct, nor desired effect. Sometimes, it just outright makes things worse. My advice is to roll back to 2.69. You can get it from the Blender website.
Here is the link - http://www.blender.org/features/past-releases/2-69/
Harry
Harry