error opening shadow group file

[Brad Crotchett]

I have a server that I cannot add users to.  Anytime I run useradd or
adduser I get the error: 'useradd: error opening shadow group file'. 
When I look in /etc I have the following files:

group
group.lock
gshadow
gshadow.lock
shadow
shadow.lock
mpasswd
passwd
passwd.lock

I blow away all of the lock files and try again, but I get the same
error and the lock files reappear.  Anyone seen this before?

Thanks,

Brad