Yellow light from power adapter and buzzing noise.

Hi,

Just recently my iBook power adapter started showing a yellow light instead of the orange-ish color (that shows when the battery is charging normally) and was buzzing when it was that yellow color. It also shows the battery in the status bar, that it is plugged in but still loses power. The status it shows kinda makes it look like its at full charge. It charges fine when set in a certain way but if it moves just slightly it starts buzzing, the power adapter turns yellow, and losing power. Battery does charge and is fairly new. Any of ideas what might be my problem? Please help, this is my school computer and its such a hassle having to make sure its charging correctly and having to prop it perfectly takes forever.

Thank you,

Andrew D.