For the record, Chris Green said he thought it would be ok to run it without the bottom, it isn't ok to do that because of the way it was designed the bottom plate directs airflow around the hard drive and cd drive.
I found an unboxing video on youtube and i asked the poster if he had the same problem and he said he did so i think a replacement would do the same thing. I think it is a design flaw.
im not sure if you still want an answer but i have had this problem twice the first time the power supply chip for the gpu (i believe that is what it is) had become unsoldered if you search on google for iBook g4 schim it will show you how to fix this problem without any soldering but it doessnt always work. the second time this happened was about a month ago my iBook fell of my desk when the power cord got tangeled with my backpack, i guess there is a point to those magsafe adapters. anyway i had just bought a 20 inch samsung display for my iMac i tried it in my iBook and it works like normal but if you do this you need to install screen spanning docter (just google it) to get full resolution. so i took my iBook apart for the hundredth time and removed the whole screen (i had done it before with a iBook g3) but i had to take the airport antenna from the screen and leave them to go out where the rest of the cables would go but it works great as a desktop now. reply if you want instructions on how to reove...