If the device isn't charging, perform a hard reset as described in the frozen - screen section above. (hubpages.com)
If you're experiencing larger problems with your device, or if the smaller problems continually pop back back up, you can perform a hard reset by doing the following: (hubpages.com)
Before performing the hard reset, make sure to charge your Kindle Fire for approximately 30 minutes. (kindlefireworld.net)