Samsung Duos B7722 - charging problem


Its Me only.
I am facing a strange problem with my Samsung Duos B7722, dual SIM touch screen phone. It is not getting charged when I connect the charger, but will get charged if I connect it after switching off my phone. It will show an indication that the phone is getting started up, but it will not, and gets charged in 3-4 hrs. After that it will not start up directly. I need to remove the battery and SIM, replace them and then it will start up. I dont know whats behind this, but its really weird. I tried for a firmware upgrade, but its showing that there is no upgrade possible for my phone. Any help..?