if u are running shadowed passwords it might be theres no entry for this user. make a backup of /etc/shadow, delete /etc/shadow and convert /etc/passwd using pwconvert.same goes for /etc/groups.
I got this error when logging in as root into a system that I think was badly installed (by me). Anyway, this fixed that problem. I found it interesting that this came up #1 on the google search and it’s an entry dated May 2001.
Note: The linux command pwconv replaced pwconvert sometime during these last ten years.
Note2: Here’s a more modern (3 years old) explanation tmhat I found useful.
Note3: I still had to do a complete reinstall since a lot of things went haywire. I probably shouldn’t have been playing with hot swapping while the install was in progress.
Update:I don’t think the kernel likes this motherboard. Second install failed. Have to resort to compiling a kernel by hand. What started out as a simple hour long task will now take all night.