I'm having a problem with Weight Painting!

I am in the process of Rigging and Skinning my model.

Here is my problem: : :spin:(I will use the left arm for example) When I move the left arm down and Weight Paint the deformations it works great, but when I move the right arm down and Weight Paint it, it moves the mesh object into the position of a flipped mirror image of the left arm! It’s like it is reffering to some sort of x-axis mirror of the left arm!

I may have caused this problem before I did the Weight Painting, by applying the mirror modifiers of each mesh object, so I could move the armature independently.

Is there a way to fix this?