Did you reboot?
After doing all the usual song and dance of rebooting, button pushing, calling customer support, and turning off and on the modems and routers; what seems to finally work for my Nook Tablet is a hard reset.
Push and hold both power and home buttons at the same time until you see the reset or continue option on your screen. Push the home button; n, and let the tablet wipe all previous data. Then re-register the tablet.
Download any past purchases and turn off the wifi on the tablet when you are done.
I believe going on certain web sites may affect the tablet after a reboot.
I was wondering if there is an anti-virus or internet security for Nook?