Executing a user created function twice give an error

Hi,

PostgreSQL 8.1.11

I have created a function that works fine when run for the first time after that it gives an error until I open another
Querywindow. 

The function is as follows

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CREATE OR REPLACE FUNCTION func_snappointtonetwork(p_pointtobesnapped "varchar", p_currentboundingbox "varchar")
  RETURNS text AS
$BODY$
DECLARE
    v_geom bytea;
       v_snappedPoint varchar;
    v_HAPMSSection varchar;
    v_road varchar;
    v_area varchar;
    v_cWay varchar;
    v_cWayDirection varchar;
BEGIN
    SELECT hapms2.sect_label as link_Id,distance(hapms2.geom,ST_GeomFromEWKT(p_pointToBeSnapped)) as distance
    INTO TEMPORARY TABLE __distances__temp
    FROM public.hapms_road hapms2  WHERE (hapms2.geom && ST_box2d(ST_GeomFromEWKT(p_currentBoundingBox)));

    SELECT INTO v_geom,v_HAPMSSection,v_road,v_area,v_cWay,v_cWayDirection
    asEWKB(hapms1.geom),hapms1.sect_label,hapms1.roa_number,hapms1.area_name,hapms1.funct_name,hapms1.direc_code
    FROM public.hapms_road hapms1
    WHERE (hapms1.geom && ST_box2d(GeomFromEWKT(p_currentBoundingBox))) AND distance(hapms1.geom,
GeomFromEWKT(p_pointToBeSnapped)) < all  
    (SELECT distance FROM __distances__temp WHERE public.hapms1.sect_label <> link_Id);

    SELECT
ST_AsEWKT(ST_line_interpolate_point(ST_LineMerge(ST_GeomFromEWKB(v_geom)),ST_line_locate_point(ST_LineMerge(ST_GeomFromEWKB(v_geom)),ST_GeomFromEWKT(p_pointToBeSnapped))))
    INTO v_snappedPoint;

    DROP TABLE __distances__temp;

    RETURN v_snappedPoint || '|' || v_HAPMSSection || '|' || v_road || '|' || v_area || '|' || v_cWay || ' ' ||
v_cWayDirection;
END;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION func_snappointtonetwork(p_pointtobesnapped "varchar", p_currentboundingbox "varchar") OWNER TO postgres;

///////////////////////////////

Error:

ERROR:  relation with OID 100412 does not exist
CONTEXT:  SQL statement "SELECT
asEWKB(hapms1.geom),hapms1.sect_label,hapms1.roa_number,hapms1.area_name,hapms1.funct_name,hapms1.direc_codeFROM
hapms_roadhapms1 WHERE (hapms1.geom && ST_box2d(GeomFromEWKT( $1 ))) AND distance(hapms1.geom, GeomFromEWKT( $2 )) <
all(SELECT distance FROM __distances__temp WHERE hapms1.sect_label <> link_Id)" 
PL/pgSQL function "func_snappointtonetwork" line 14 at select into variables

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Any help in this matter would be highly appreciated.

regards,

W Khattak