Daedros Endus,
Switch your layer name for the international string variable.
Code:
<Bindings>
<Layer name="SI_KEYBINDINGS_LAYER_GENERAL">
<Category name="Custom Bind">
<Action name="MAGIC">
<Down>MagicStart()</Down>
<Up>MagicStop()</Up>
</Action>
</Category>
</Layer>
</Bindings>
That way your key bind will still work if the end-user is playing in French or German. There is also one for the Category. That is "SI_KEYBINDINGS_CATEGORY_USER_INTERFACE".
-Cheers