Have you ever turned on your camera to find the following message: "Card Error"? And all of your photographs have disappeared? You are not alone. Your memory card has failed. All media will fail at some point, we don't know when it will happen only that it will. If you find that your card has failed. STOP using your card. DO NOT reformat it. Leave it alone until you get home. You may be able to recover the information with some simple software. Here are a few sources for data recovery software

http://www.cgsecurity.org(free)
http://www.cardrescue.com/ ($)
http://www.lexar.com ($)

Many digital cameras allow you to change the "ISO" or sensitivity setting. Most models will default to a lower setting, usually around 100. When shooting in low light try increasing the ISO. The higher the ISO is set the more it will gather the existing light and allow you to shoot with faster shutter speeds. Beware, that the higher your ISO the more image quality you'll sacrifice. Try experimenting at different ISO's, as every camera has different capabilities with varying results. Also note that on many modern digital cameras, AUTO ISO is also a good choice. In some models you will even be able to set the upper limit.