ember-cli command only works the first time

Hello,

I've been using ember-cli on my Windows 8 laptop. Running ember-cli-windows only improves the build time the first time that I run the command. If I restart the machine, the server goes back to being very slow and re-running the ember-cli-windows command makes no difference. However, the commands behaviour changes. Whereas it runs without issue from cmd the first time it is run, subsequent runs opens the power shell and the "Defender Configuration not available error..." is shown.

I have no idea how to debug this so any suggestions would be most welcome!