cygz.dll not found.

Hello,

I installed PostgreSQL on my Windows pc. It is working as a service.
When i want to execute a pg_dump <databasename>  <filename>, I get the
message cygz.dll not found.
I installed postgresql via PgSQL731wina1 that contains an installation of
cygwin.
What did I wrong of must I install other software.

Thanks for your time.

Max.