SPI_execp() failed in RI_FKey_cascade_del()

Hi,

In my database there is a table "request" which is referenced
by a couple of other tables (about 4 or 5). Since quite frequently 
I need to delete "request"s with any related data, I formulate
the foreign keys in the following way:   

     request_id INTEGER
      CONSTRAINT n_request_id NOT NULL 
      CONSTRAINT f_request_id 
       REFERENCES request ON DELETE CASCADE 
       DEFERRABLE INITIALLY DEFERRED,

Here comes the definition of "request":

CREATE TABLE request (
 request_id    INTEGER 
  CONSTRAINT d_request_id DEFAULT nextval('s_request_id'::text)
  CONSTRAINT p_request_id  PRIMARY KEY,
 label         TEXT  CONSTRAINT n_label NOT NULL,
 description TEXT ,

 announce_date DATE CONSTRAINT d_announce_date DEFAULT CURRENT_DATE,
 submit_date   DATE CONSTRAINT n_submit_date NOT NULL,

 mail_subject TEXT ,
 mail_message TEXT ,

 organization_id INTEGER 
  CONSTRAINT n_organization_id NOT NULL 
  CONSTRAINT f_organization_id REFERENCES organization,
 questionnare_id INTEGER
  CONSTRAINT n_questionnare_id NOT NULL 
  CONSTRAINT f_questionnare_id REFERENCES questionnare,

 status "char" 
  CONSTRAINT x_status 
  CHECK (upper(status) IN ('S','A','O','C','E')),
-- [S]aved, to-[A]nnounce, [O]pen = announced, [C]losed, [E]rror
 participated INTEGER CONSTRAINT d_paricipated DEFAULT 0,
 asked  INTEGER ,

 CONSTRAINT x_request_dates CHECK (submit_date > announce_date)
)
WITHOUT OIDS;

and when I execute the query "DELETE FROM request WHERE ..." I got
the following error message:

ERROR:  SPI_execp() failed in RI_FKey_cascade_del()

My questions:
- Is it connected to permission somehow? 
  (delete revoked some of the related tables)
- What to do to get work the cascaded delete?

(with version 7.2.1 of postgres as a database superuser (postgres))

Gyozo Papp 
- pgerzson@freestart.hu