Weight Painting is turning my Mesh inside out... Why?

Hello, I’m a Blender noob trying to learn the ropes in 2.49b. I’ve worked through almost all of the Essential Blender tutorials, and the BSOD Intro to Character Animation, so I feel comfortable with the basics. I’m having a weird problem though.

I’m working on a simple rig for a mesh I pulled from a computer game (Torchlight), and when I tried weight painting on the mesh, everything worked out fine except for the lower legs, which apparently were turned inside out when I painted them, as shown here:

Before:
http://i52.tinypic.com/6zrfaw.jpg

After:
http://i54.tinypic.com/eur9xd.jpg

The only thing I did between taking these screenshots was weight paint the legs.

The feet, upper legs, body, arms, and head all turned out fine. Does anyone know what could be causing this problem?

EDIT: I did some more tests by painting the entire mesh to the lower legs, and the mesh crumpled up like a piece of paper. It doesn’t do that for any of the other bones, so I’m pretty sure it’s a problem with one of the settings on my lower leg bones. But I have no idea what setting would have that effect.

Maybe to the more experienced users I might sound like an idiot ( I am still learning how to use blender ) but have you tried recalculating normals. If that don’t work try deleating your current rig and re-rig your character