I think I need to paint the right ear, because the Ear.L is the side that is mirrored?
Hi Xavier,
Because there is a mirror modifier on the mesh, you will only be able to paint the side where the vertices are 'real'. (which I think is the left hand side from memory)
However, don't forget that the mirror modifier can't create the .R vertex group for you. It can mirror the weights, but you need to already have a home for the weights to be mirrored into.
Hope that makes sense.