Support Ticket
Trying to rename http://grouppatternlanguage.org/wagn/Going_Meta to "Go Meta". Hoptoad says:
ActiveRecord::StatementInvalid: PGError: ERROR: duplicate key value violates unique constraint "cards_key_uniq" : UPDATE "cards" SET name=E'Go Meta+discussion', "key"=E'go_metum+discussion' WHERE (id = 4093) and ActiveRecord::StatementInvalid: PGError: ERROR: duplicate key value violates unique constraint "cards_key_uniq" : INSERT INTO "cards" ("name", "reader_type", "indexed_content", "updated_at", "appender_id", "current_revision_id", "created_by", "references_
This is ticketed here: http://www.wagn.org/wagn/don_t_let_trashed_plus_cards_block_renaming
You can work around by finding out the trashed card causing the problem (eg "Go Meta+discussion"), re-creating it, renaming it to something harmless, and then deleting it.
I fixed this issue that way.