PL/pgsql

Hi can any one help me out with the following trigger that I have
written....

CREATE FUNCTION new_site() RETURNS OPAQUE AS '
BEGIN
IF NEW.SITE_REFERNCE = SITE_REFERENCE
THEN
SITE.END_DATE := NEW.START_DATE
SITE.CURRENCY_FLAG := 2
END;
' LANGUAGE 'plpgsql';

CREATE TRIGGER NEWSITE
AFTER INSERT ON SITE
FOR EACH ROW
EXECUTE PROCEDURE new_site();

the trigger enforces versioning of new sites inserted into the site
table of my land_use database....
but after defining the function I can no longer insert new sites into
the database.

i receive the following error from psql:

ERROR: fmgr_info: function 56664: cache lookup failed

when I try to insert the following data:

INSERT INTO SITE
(SITE_REFERENCE,UPRN,LA_REFERENCE,VERSION_NO,CURRENCY_FLAG,START_DATE,END_DATE,EASTING,NORTHING,PAO_DESCRIPTION,STREET_DESCRIPTION,LOCALITY_DESCRIPTION,TOWN_DESCRIPTION,POSTCODE,LA_CODE,AREA,LAND_TYPE_REF,LAND_USE_DIVISION_REF,LAND_USE_CLASS_REF,LAND_USE_SUB_CLASS_REF,DERELICTION_REF,OWNER_REF,PLANNING_STATUS_REF,PROPOSED_USE_REF,HOUSING_COMPONENT,HOUSING_SUIT_REF,MOST_SUITABLE_USE_REF,EST_HOUSING_CAPACITY,HOUSING_DENSITY,LEGAL_CONSTRAINTS,PHYSICAL_CONSTRAINTS,AVAILABLE_ON_MARKET,AGENT_NAME,EP_RDA_INVOLVEMENT,GENERAL_SITE_INFORMATION,BOUNDARY_ID)

VALUES (345600001,null,null,2,1,'20020311',null,414722,130160,'57 TO
61','GREENCROFT STREET',null,'SNAILSBURY','SN3
5BX',3456,0.062,2,11,44,133,11,3,4,2,4,1,2,10,161,1,2,3,null,2,null,3456000011);