Can't login as normal user...only as root

[zipper]

I'm not sure what has caused this problem, but over the past few days, my family members have been unable to login as normal users on my laptop. I normally don't use the laptop, so I haven't observed this issue until now. I can login to Gnome as root, but not with my normal password. Boot up till the login screen appears to be normal. When I enter my user name and password I get the following message:

"GDM could not write to your authorization file. This could mean that you are out of disk space or that your home directory could not be opened for writing. In any case, it is not possible to log in. Please contact your system administrator."

As root, I uninstalled a bunch of applications and went through my son's home directory and deleted all of his pictures, but after reboot it still does not allow normal log in. Any idea what could have caused this problem and how to fix it?

Thanks,

[sailor]

Could it possible some sort of corruption in the profiles or user files? Or some permissions problem?
It has been suggested to remove your user and your home folder, backing up necessary folders/files (like the Firefox folder ), and then just adding the user again.

[nix4life]

Check your authentication method. You might have accidently enabled KERBEROS/SMB/LDAP?

[zipper]

Thanks sailor for your post. I've backed up the data in the user's home directories, deleted their current user and created new ones. Now it is working again.