can't lock password file

[Gerry Creager]

I just tried to add a new user and when we run passwd, I get a message
that says,

Cannot lock the password file; try again later.

The installation is Slakware 3.4/2.0.30 with shadow passdword enabled
(by default).  I don't recall doing anything that messed with /etc or
/etc/passwd, so I'm at a loss...

TIA,
Gerry Creager
Mapping Sciences Laboratory 
Texas A&M University