Like OBCD said, did you choose the correct kernel when you set up Ndure? I remember reading a blank screen can result from choosing the incorrect kernel. Since you've got a solid green light it sounds like you're not too hosed.
Can xboxHDM still see the drive if you hotswap again? If so, try going through the ndure setup again and make sure you choose the correct kernel.
Just my 2c. I only started softmodding last week so don't assume I know what I'm talking about
