PLS-00431: bulk SQL attributes must use a single index

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PLS-00431: bulk SQL attributes must use a single index
ORA-06550: line 15, column 37:
PL/SQL: ORA-00904: : invalid identifier

If you got a message like this, perhaps you tried to execute or compile a
PL/SQL program containing a statement like the following:

DECLARE
TYPE NUM_TAB IS TABLE OF INTEGER INDEX BY PLS_INTEGER;

COLL_OF_FLAGGED NUM_TAB;
COLL_OF_ORDERS  NUM_TAB;
COLL_OF_PARTS   NUM_TAB;
BEGIN
...
FORALL x IN 1..COLL_OF_FLAGGED.COUNT
UPDATE order_parts
SET is_damaged = 'Y'
WHERE order_id = COLL_OF_ORDERS(COLL_OF_FLAGGED(x))
  AND part_id = COLL_OF_PARTS(COLL_OF_FLAGGED(x));
...
END;

I highlighted in red color the cause of problem: nested collection indexes.
FORALL cannot cope with nested collection indexes on 10GR2 and earlier (on 11G i didn't tried yet), which means that you will need to rewrite the statement as a non-bulk UPDATE loop structure:

...
FOR x IN 1..COLL_OF_FLAGGED.COUNT
LOOP
UPDATE order_parts
 SET is_damaged = 'Y'
WHERE order_id = COLL_OF_ORDERS(COLL_OF_FLAGGED(x))
 AND part_id = COLL_OF_PARTS(COLL_OF_FLAGGED(x));
END LOOP;
...

or alternatively you might want to modify the table structure and "demote" the pair (order_id, part_id) to a simple unique constraint, while creating a single column primary key based on a sequence number, which would probably allow you to rewrite the statement above in the following way (assuming that the collection COLL_OF_FLAGGED contains the new primary key values):

...
FORALL x IN 1..COLL_OF_FLAGGED.COUNT
UPDATE order_parts
 SET is_damaged = 'Y'
WHERE order_part_id = COLL_OF_FLAGGED(x);
...

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