Casio exilim camera?

i just bought a casio exilim 7.2 megapizel camerathats red, and i read the instructions an it said the battery should chare in 90 minutes. well its been like 4 hours an its not charged. the lil light is blinking that says charge but it said when its done the light will go off, is it even suppose to blink? whats wrong!?