Thank you very much, I will check that as soon as possible ;)
I finally had some time to experiment (because I had of course some troubles to install the virtual machine).
On the vm everything is ok, so I will check the differences and retry to install it on my real machine (first of all, on the virtual machine, I have only installed grunt-cli globaly and no grunt).
Not much, still stuck with my error.
But, I don't know if its new or if I didn't notice before, but there is a previous error : "Error downloading the framework npm ERR! path c:\adapt_learning\temp\…\adapt_framework\grunt". But two line before the git was cloned successfully :/
Meanwhile I can try adapt in the VM, but the error is really annoying because everything seams identical :/