Connection terminated

Hi
I am running postgres locally. All was working well.
I can start postgres using the command line which says:
>postgres successfully started.

but when I  type in the command
>psql -U nameOfUser
psql: server closed the connection unexpectedly
    This problem means the server terminated abnormally
    before or while processing the request.

I have checked In postmaster.log which says:
DEBUG:  database system is ready
I have checked PGDATA, PGHOME and PGHOST which all have the correct path.
I have checked postgres in the current processes running,ans that psql is on
it path.
Why can I no longer run psql?
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