IBook won't boot into OS X

Question

Hi
I was using my iBook the other day when the screen unexpectedly went gray, it then went into standby shortly afterwards and would not power up. A three-fingered and power-switch salute later, and I was back at the login screen, but it would not boot into my admin account on OS X after that -- just a blue screen (sometimes with the background image preserved).
A visitor account on the same machine boots fine.
I have been over the disk with DiskWarrior, repaired permissions and the drive with Disk Utility, reset the login plists (under single user command line startup) and done the other relevant tasks for 10.4.4 as detailed in
http://docs.info.apple.com/article.html?artnum=106464
Na da.
The suggestions at
http://docs.info.apple.com/article.html?path=Mac/10.4/en/mh2235.html
are no use because even when booting into safe mode, the OS won't start.
There are no accessories plugged in, no external drives, USB devices (inc keys) or networks wired or wireless. No software has been added in recent days other than a recent minor upgrade of the Apple Backup software that was released the other day. No new firmware is required.
The machine was working just fine and went on the fritz with no warning. It was sitting quietly for a few minutes having received no recent input from me or any outside source that could have precipitated the meltdown.
AFAIK I have exhausted the Apple knowledgebase on this and similar issues. I can find no other resources or clues on the net to fix the problem.
Anyone have any clues as to what the cause and, most importantly, solution is?

Answer 1

Sounds like the OS is starting just fine. Your login account, however, has some problems. I'm assuming you aren't using an encrypted home directory, so it is probably something simple like a corrupted preferences file for Finder or Dock or something.
When you are logged in as an ordinary user, navigate into the Admin user's home directory if you can. Go into the Library folder, then drag the Preferences folder out of the Library folder into the home directory. It should ask you to authenticate because you don't have permission to do that. Enter your Admin username and password.
Once the directory is moved, log out of the guest user and log back in as the admin user. You should be able to log in successfully. At that point, if you'd like, you can move individual preferences files from the old preferences folder into the newly-created Preferences folder (in Library).