I found that my easy populate was doing exactly the same thing (was booting me back to the login) and I to spent sometime looking through this post and found the replies to yours, I found that it was only booting me back to the login when my shop was not in the root directory (e.g. www.myshop.com/catalog/) as soon as I moved the shop to my root directory(e.g. www.myshop.com/) easy populate worked fine!
THANK YOU!! :)