My LG Optimus L9 is stuck on a white encrypting screen.. How can I fix this?

[AC Question]

My phone died and when I went to plug it in and turn it back on a white screen showed up with "Encrypting" in blue letters at the top of the screen. A status bar or something is underneath it and there is a 'reset phone' button in the middle of my screen. Nothing I do will get rid of this screen and I cannot use my phone. How can I fix this, or do I just have to leave it alone and see what happens?