error: duplicate key - Mailing list pgsql-admin

I am receiving this error when I try to add new records:

INSERT INTO "public"."classification_guide_cats" ("id", "cat_title") VALUES (nextval(('"classification_guide_cat_id_seq"'::text)::regclass), 'temp')

SQL error:

ERROR:  duplicate key violates unique constraint "classification_guide_cats_pkey"

id is a primary key nextval(('"classification_guide_job_id_seq"'::text)::regclass)

Could the primary key count have been reset so that it is starting at 1 again? The primary key id is up to 128.

Thanks

Marc