So it was working for 3 days, and now it keeps on hanging on start?
Could you try and Factory Reset it?
Push the stylus on the small reset button on top, and hold it for some time, 15-20 seconds should be enough. (Not sure how long you need for a complete reset, I usually count slowly to 20. ;-)
It should then reboot and you should get to the initial settings.
See if that helps, if you after this still directly get stuck on boot, I would recommend you contact support as you might have a defect unit.
If you can boot, and configure the router, let us know if you again get trouble after a few days, as there might be something else going on.