Hi, Greg,

Welcome to the forums.  You have a great question and I have seen this come up before.  Your problem, more than likely, is caused by memory problems.  To be exact, not enough memory.  Go to Options>Memory and see how much free memory you have on your SD card.  If you have your pictures by default being stored on your SD card and there is not much room left, it can cause a problem with the camera not working.  The cure is to buy a bigger card.  Also, if your device itself does not have much memory left, it will cause problems.  You can check your device's main memory at Options>Status and see how much is in File Free.  You can free up main memory by deleting apps that you do not use very much.  Anyways, I hope this helps.

Doc