Thank you,
I have the last version of the theme and despite the tips of global.asax the problem still here...
Version nop-commerce 3.60
Visual Studio 2013 (12.0.31101.00 Update 4)
When I want to access to the preferences of ArtFactory (thru Plugins > 7 Spikes Themes > ArtFactory > Settings) I'v got this error on local test :
And when I test on my production server I'v got this one :
Thanks by advance for your help :)