where the batteries sit most cameras have a spring loaded config. so they sit tight in the compartment it may well be one of these has flattened out so one of your batteries is not connecting properly,
if you open the lid where the batteries go you might see one of them sitting lower than the others, use what you can to try and revive the spring loading,
this may help,it's exactly what happened to mine
(samsung digimax) pulled my hair out for a while then worked out what it was,good luck......