According to Campbell's demand (see email below, bpy.context.scene issue) and 
the last message in the tracker 

http://projects.blender.org/tracker/index.php?func=detail&aid=31618&group_id=153&atid=468)

I have changed the code. 

Blendphys.


******************* Campbells email from 20.12.2012 03:38 ********************

Recently I've noticed addons using bpy.context.scene when being
imported or in the register() function.

This is really bad practice and will cause inconsistency if the addon
is enabled and a different blend file is loaded.
In the worst case accessing a removed datablock can crash which is
likely if a datablock is stored as a global variable on activation -
object_laplace_lightning.py does this.

I've changed addon loading so that they only get access to a
restricted context which only exposes 'window_manager' - needed for
adding keymaps.

.....