If you've munged your template1 database, you can rebuild it from the template0 database.

First, you must set the datistemplate attribute of template1 to false so we can drop it:

xinu=# UPDATE pg_database SET datistemplate = false WHERE datname = 'template1';
UPDATE 1
xinu=# DROP DATABASE template1;
DROP DATABASE

Next, re-create template1 using template0 as a template:

xinu=# CREATE DATABASE template1 WITH TEMPLATE = template0;
CREATE DATABASE

Then restore the datistemplate attribute of template1:

xinu=# UPDATE pg_database SET datistemplate = true WHERE datname = 'template1';
UPDATE 1