iBook G4 not booting

Help.

I've got a G4 iBook running 10.4.8.
I've had no problems whatsoever with it until very recently.
About a week ago I started to think I might need a new battery as the charge wasn't lasting very long.
Then suddenly a couple of days ago, after about an hour of use everything froze.
I mean everything.
No shortcut keys worked, mouse didn't move, couldn't force a shut down.
Eventually I had to resort to removing the battery.
I was only running Firefox at the time.
Nothing too strenuous.

I put the battery back in, turned on, got as far as the grey screen with the water wheel and it froze again.

I left it overnight (to avoid losing my rag and smashing something), tried it the following afternoon and got as far as the "select user" screen before it froze again.

Thinking that maybe the battery might be dragging it down I tried running it direct from the mains but that had no effect, positive or negative.

I left it for a full 24hrs and managed to get it started up, logged in and into a finder window with the intent of saving some files to my external drive, but before I could even select a folder it froze again.

I can't imagine it's a hard drive problem otherwise it wouldn't get in as far as my account.
I can't imagine it's a motherboard problem otherwise it wouldn't boot at all.
And I can't imagine it's a battery problem otherwise running it from the mains would improve the situation.

I haven't installed any new apps or significant updates recently so it can't be anything software related.
And I get the same results booting from the OS DVD so I can't imagine it's a corrupted boot file or anything of the sort.

Anyone seen anything like this before and have a possible solution?
It's driving me nuts.

Thanks in advance.

It's very likely a hardware problem and could be a flakey logic board that's acting up. Since you can't boot with your install DVD and do a check on the hard drive there's no way to tell if that has problems or not. Kind of difficult to trouble shoot.

Something you can try... is if you have access to another Mac that has a firewire port, you might be able to access your iBook from the other Mac by using the Target Mode boot method. That at least might let you get your data from the hard drive to a safe place.

One other thing... some of the older iBooks have been known to have problems similar to yours when the PRAM battery went dead or very weak. If your machine has been around for awhile that's something to maybe consider. According to the above site the PRAM battery for the iBook G3 is built into the external battery. I don't know if that's true for the G4. You may need to do some additional research.

Regards.