There is a fix.
I ran into this problem with my PowerBook. My other Mac's were ok.
Step 1: Boot in single user mode (Single user mode bypasses the GUI, which is all the visual stuff, and gives you something called "root access") by pressing Command + S (Apple+S) when the first shade of blue appears on the screen, and holding it down until the screen turns black with white text.
Step 2: Wait for all the code stuff to load. Now, the first thing we need to do in single user mode is mount the hard drive so we can edit it. You enter this command in : /sbin/mount -uw /
It should say something about removing orphaned unlinked files.
Step 3: We are going to delete a little file that tells your computer every time you start up that you've completed the setup by entering this commmand: rm /var/db/.applesetupdone
It should just bump down, waiting fotr the next command if it worked.
Step 4: Now type, reboot
Step 5: It should shut down and reboot. Than, a setup window will appear, asking you what language you want your computer to be in, just like you see when you setup a newly purchased Mac.
WARNING: A welcome video will play after you select the language. It has some pretty cool music, but if your in a room with other people, I'd mute it right after the video starts.
Step 6: Setup the computer. Select "DO NOT TRANSFER MY DATA". Don't worry, all your old stuff will still be there. Choose your internet connection and network, here is where you need your WEP or security password if you have one.
Step 7: Create a new local account to administer that computer. You usually want to enter the name of the computer as the longname, and the shortname what you'll log in as. Say your computer's old name was "Frank's Computer", than just put Frank as the longname, because it will automatically as "'s Computer" at the end. MAKE SURE THAT BOTH USERNAMES ARE DIFFERENT FROM THE EXSISTING ONES, OTHERWISE IT WILL OVERWRITE.
Step 8: Finish the setup, and you should automatically be logged into your new administrator account.
After logging into your admin account, go to system preferences and open the accounts pane. Select your old account and enable it as an admin account. Logout of the one you have just made and re- login using your original account. You now should be an administrator again. You can go back to system preferences and delete the account you made in the exercise.
ps - in step 7 it is really important about the account names. I used BillyGates as mine.
aussie_geek