PowerBook Battery

I have a PowerBook G4 which I love dearly. It has been working perfectly until now. I noticed yesterday when I started it that the battery icon in the menu bar had a cross though it and when I clicked on it, it told me that there were no batteries available - I have not touched the battery in the three months I have had my PowerBook!
I have had it plugged in to a power source and the connection glows green - however as soon as I unplug it the computer dies and the date and time reset when I restart it after I have plugged it in. Clearly it isn't charging and I don't know why.

Can anyone tell me why I can't my computer isn't charging?? Is there something seriously wrong with it??

Thanks

I think you should go to the Apple.com support website and read up on how to RESET THE POWER MANAGEMENT UNIT. There's a section for it in the Powerbook help topics.