useradd: unable to lock password file

[list at everywhereinternet.com (Nick)]

Hi,

Help. I have an issue adding accounts to a centos box of joy that has
otherwise been 100% reliable. 

Basically if I run a "useradd test" as root it returns useradd: unable to
lock password file.

There is a /etc/passwd.lock file:

[root@bill etc]# more passwd.lock
6697

  PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME CPU COMMAND
 6697 root      25   0 22672  22M   612 R    47.2  1.1   1:02   1 useradd

Eating lots of cpu... but doing what?

If anyone has any clues I'd really appreciate the help :)

Cheers,

Nick