more info would certainly help. The green light only isn't a clear indication that your ibook isn't getting any charge- it could be getting a trickle charge or the amber light might not be working properly. I suggest looking at the input output voltages with the charger plugged or unplugged (use xbattery or xresource graph or similar). that might help you diagnose a battery problem if that ends up being the case as some have suggested.
the charging plug certainly takes abuse over the years so I wouldn't rule out a short at the computer where the charger plugs in, if you apply sidways/up-down pressure to the adapter at the computer does the amber light come on?
good luck and repost with more info if you are still trying to resolve this.