Rechargeable batteries are good for about 500-1000 charges. Some manufacturers recommend conditioning batteries after every 10 or so recharges. It helps keep the capacity of batteries from diminishing. If you've never conditioned yours in two years, they are probably no longer capable of charging anywhere near their original full capacity.
Condition by draining batteries completely of power, then fully recharge. For example, keep your camera on until it completely shuts off by itself. If your LCD turns off automatically, shut off the setting so it stays on. If conditioning doesn't improve how the batteries hold charge, it is probably time for a new set!
I do recommend you buy an set of alkaline batteries first and see if things improve. Is so, then you know that low battery power is the root of the problem. Remember, too, that digital cameras drain alkaline batteries fast, so don't expect them to last very long.
btw, some rechargers condition batteries automatically.
Related reading:
Digital camera batterieshttp://www.digicamhelp.com/digital-camera-batteries/digital-camera-batteries.htmBattery rechargers:http://www.digicamhelp.com/digital-camera-battery-chargers/index.htm