Create Extension search path

On my windows install of postgres 9.1.0.

I have a search_path set in the config file. This search path has
several schemas defined.
Some of the databases within postgres, do not have the schema specified
on the search path defined within the database.

Trying to add pgcryto via:
CREATE EXTENSION pgcrypto;
or
CREATE EXTENSION pgcrypto SCHEMA public;
Fail with the error invalid value for parameter "search_path".

To add the extension required me to change the search_path.
Is it required that all any schema added to the search_path exist in all
databases?

Thanks,
Roger