This means the built-in 8MB of WPZ2 camera memory is full. This 8MB is only enough to take a couple of 'test' photos on your WPZ2. We recommend purchasing a standard microSD/microSDHC memory card that is at least Class 4 and no larger than 32GB.
If you are using an microSD card and receive the message, that means that the microSD card is full.
You will need to use a different microSD card or delete photo and video files from the microSD card in order to create more usable memory.