@readandforget: You're in the wrong thread, and thus followed the wrong instructions for a PaperWhite.
The PW thread explicitly mentions doing the initial configuration with a shell on hand, and *never* rebooting before checking that everything is working.
Depending on what you have installed (USBNet/Rescue Pack), you have different ways of getting your Kindle back on track. See the first page of the PW thread for the nearly-last-resort fallback, and
this one for the really last-resort, since that's a factory reset.