Is the X red or black? There are 7 models in the A1181 series, please remove the battery and give us the specific machine so we can direct you to the correct part and service manual.
Download and run Coconut battery to see the status on it first: http://www.coconut-flavour.com/coconutbattery/
My first guess is the battery connector, but lets see the results of Coconut: http://www.applecomponents.com/items/0000002400/922-8129_battery-connector-with-sleep-switch/