How to copy weight painting on foot1 to foot2? I have a mesh (half a human body) and an armature, which is mirrored by scaling -1 along x, and then fixing bone roll. The mesh is weight painted. 
I want to mirror the mesh. However when I use the mirror-modifier, I experience great problems with the feet.

When I mirror the mesh, the weightpainting of the feet get copied. In the sense that the foot-bones for one of the feet controls both feet, while the other doesn't control any. The rest of the rig works fine.

How do i make the feet-bones control each their feet?

This is my modifies for the mesh
It seems to me that the new foot bone is either using the group associated with the other foot or that it copied a new group to the new foot but has also copied over the weights for the opposite foot...

You need to make sure that you have a separate group for each foot bone, and that each of those groups is associated with its particular foot weights.

Its also good to keep good naming conventions, foot.R and foot.L, for your bones and groups as blender uses the .L or .R to work out its symmetry when doing opposite calculations.

Hope this helps...