Lockups are not uncommon with new firmware. The EZ Reader firmware is not currently available due to the web site being redone but you can download the latest from Hanlin from the Jinke web site. It is pretty stable although you won't have the Astak splash screen.
A reset can normally be accomplished without removing the battery. There is a hole in the back that performs a reset if you poke a paper clip through the hole. You can also reset the device by holding the power button down for about 10 seconds.