Can anyone help with the following problem

Ive created a package with the following SQL

IF title_level = 'P' THEN
BEGIN
SELECT od.description
INTO description
FROM object_descriptions od,
V_P_TITLE_LEVEL ptl
WHERE od.obj_id = ptl.prg_auk
AND od.type = 1
AND ptl.ss_box_cod = TO_CHAR(ss_box_cod);

EXCEPTION
WHEN NO_DATA_FOUND THEN
NULL;
END;
RETURN;
END IF;

running it results in error ORA-01422
'exact fetch returns more than the requested number of rows'

I can understand this error if more than one row is returned, but running the sql as follows

SELECT od.description
FROM object_descriptions od,
V_P_TITLE_LEVEL ptl
WHERE od.obj_id = ptl.prg_auk
AND od.type = 1
AND ptl.ss_box_cod = TO_CHAR(1711634270);


returns just one row

**ss_box_cod is equal to 1711634270 when run inside the package.
V_P_TITLE_LEVEL is a view

tia