Battery Calibration not working

Hi there, I have a white macbook (2.4ghz, 160gb hd) I bought last August. Suddenly the battery only lasts for 2 to 2.5 hours. I have calibrated it twice as per the apple instructions - the first time the calibration worked (about a month ago) but when I calibrated it again yesterday it hasnt made any difference. Also, when I am charging the battery both the macbook and the magsafe charger are getting extremely hot. Have I got a dud? or am I doing something wrong??? I am new to macs and also this forum..so all help is very gratefully received!!! Thank you.