Prius (2004-09) :: Check Engine Light And Clicking - 12v Battery Dead?

I went out in the 9 degree temp this morning to start my car and take off for work. I sat down and hit the power button and some console lights came on. The gear lights were blinking with a square light around each letter (P, D, R, B...) and the pips on the fuel gauge were blinking, beeping during each blink. Also, the green light on the power button was blinking and the little light showing that the key was not in the car was also on but the key was beside me. I turned it off to try it again.

Before I turned it back on, I inserted the key in the slot and hit the power button again and just the Check Engine light came on and everything else was black. There was a slow tempo click-click-click-click... sound coming from under the hood and the Check Engine light was just sitting there. I tried to turn the car off but the power button was not doing anything. All I could do is let the Check Engine light stay on and the click-click-click-click... sound chirp away. I went back out in a couple hours and the battery was dead.

Just seeing if that might mean something specific before I go drop about $200 on a new 12v battery later today.