You didn't mention if your rechargeable batteries are new or old, or the type. Batteries need to be reconditioned every so often, ie. compelety drained of power then fully recharged again) If you don't have a charger than reconditions batteries, we have some information about how to manually recondition batteries here:
http://www.digicamhelp.com/digital-camera-batteries/rechargeable-batteries.htmRemember, too, settings such as continuous autofocus and keeping the LCD on all the time will drain batteries more quickly. Using the flash a lot also drains batteries.
