Ubuntu :: User Accounts And Groups Not Listed In Account Admin Tool?

I recently ran into a situation where the ftp user account suddenly could not login. I used the User and Groups system tool to check the user account and reset the password. I then attempted to use ftp and login with the new password and still could not. I then went to check the permissions on the folder and found that the system partition was full, so using gpartd I was able to resize the system partition.

However this still did not fix the ftp login problem. When I opened the User and Groups tool again, all users,including my main account, except root are no longer displayed and all groups are not showing. If I try to add the original ftpuser account I get the message that the user already exists. And my main account works for login still. If I add a new user, it is not displayed in the list either.

If I do a cat /etc/passwd I see all the users listed including the new one I created and cat /etc/group displays all the groups and everything looks like the users are still associated with the correct groups. I can use passwd to change the account password without error and I can use adduser to add another user. Howerver no users are listed in the User and Groups tool and users still can not login to ftp. I can reinstall proftp if needed but I would like to be able to use the User and Groups tool to administer users again.

PS: Forgot that just before encountering the ftp login problem, Update Manager and some updates listed that I attempted to install but got an error and didn't have time to check why. Now I know that the partition was full.