Disappearing user accounts

Having a problem with a fleet of iBook G4s at the school where I work...

Each of the 7 iBooks has 18 user accounts (one for each school class) and an admin account. Problem is, every few times I boot them all up to log into the account for a specific class, in time for their lesson, at least one of the accounts seems to be missing from the login window on at least one of the machines. I log in to my admin account and look under the accounts pane in system prefereces, and the account in question is still there on the list, but just not appearing in either the main login window or the list you get with the fast user switching button. It seems the only way to fix it is to delete the account and remake it, then salvage any work from it from the deleted users folder.

Any suggestions as to why this is happening and how I can fix it?

Cheers,
James

Ok I found two possibilities here. Well three in fact! One where you can use Terminal to show all users (the tip is at the end of the article) 10.4: Hide users from the login window via prefs or by using Mike Bombich's LoginWindow Manager.

And the third one being...

But from what I've read, it seems that since 10.4.2, no user name is hidden by default and should all show up in the login window so me thinks there could be something going bad with a pref file somewhere or some kind of data corruption.

There is a pref file for the Login window and you might want to trash that on a test computer in case this file is somehow important, not on a computer that you need right away, and see how the computer reacts after a restart with the pref file still in the trash. The path to this file is:

Macintosh HD -> Library Preferences -> com.apple.loginwindow.plist

Another thing you might want to try is using either MainMenu or OnyX. Both need the administrative password so students won't activate either programs by mistake or mischief (I personally use MainMenu but they are basically the same and OnyX might be a better bet for you as you can run simultaneously many scripts). You could use one of these and do the various rebuilding scripts, clean all the caches and restart, see where that takes you. But this would have to be done before classes start as the whole process can take up to 5 minutes or a bit more depending on the speed of the computer: all problematic computers could run the scripts simultaneously as the programs don't need button-slicking and someone manning the procedure.

Good luck and let us know how this goes and what works for you.