The device may just need to be restarted. The screen may be misaligned, requiring you to go into the device and straightening out. The screen may also have dirt or smudges causing misread input. The microSD card might be causing the display to accept wrong input, so restarting the device without the microSD inserted may help. There are applications for recalibrating the screen if the input is being read incorrectly. An undercharged battery might also be the cause. Recharging it may fix the issue.
[Please refer to the [[Nook Color Troubleshooting|Nook Color troubleshooting page]] for more information.