could not open relation "pg_trigger_tgrelid_tgname_index"

Hello to everybody.

I'm running PostgreSQL under Cygwin on Windows 2000 SP4.

I'm receiving the following error on ANY connection to our main database:
pgsql: FATAL: could not open relation "pg_trigger_tgrelid_tgname_index":
No such file or directory.

Connections to template1 succeed, template0 is not accepting any
connections and other test databases under the same PostgreSQL instance do
work.

I already tried restarting the service and it does well, but still doesn't
allows us connections to the main database.

I can't even connect to do a dump, so I can re-init the DB. The problem
started suddenly like 2 days ago.

Is this a known issue? I'd like to know if there is any available help and
if there is any other information useful to diagnose this problem.

Thanks in advance.

Octavio.