Fail to search in array, produced by subquery - is it a bug?

With Postgres 8.4 query like

SELECT *
FROM core.tag_links ctl
WHERE (ctl.tag_id = ANY (
SELECT array_agg(ct.id)
FROM core.tags ct
WHERE (LOWER(ct.tag) LIKE LOWER(('search tag')::text || '%') ESCAPE
E'\\')
));

produces error:

ERROR: operator does not exist: bigint = bigint[]
ROW 3: WHERE (ctl.tag_id = ANY (
^
HINT: No operator matches the given name and argument type(s). You might need
to add explicit type casts.

Bith ct.id and ctl.tag_id - of type BIGINT.

Result of

SELECT array_agg(ct.id)
FROM core.tags ct
WHERE (LOWER(ct.tag) LIKE LOWER(('search tag')::text || '%') ESCAPE
E'\\');

array_agg
-----------------------------------------------------------------------------------------------------------------------------
{54426,53600,54062,187207,187642,54395,53312,51912,128621,19203,6613,54462}
(1 row)

Should ANY (...) and ALL (...) work when "..." is a subquery, returning
single ARRAY field, or maybe I misunderstood something?

Regards,
Dmitry