unsupported types in 8.0.1

I'm attempting to upgrade to 8.0.1, and have hit my latest hurdle: an
unsupported type when I try to compare ints. Example:

gr-test=> \d invitecodes
                                Table "public.invitecodes"
    Column   |  Type   |                            Modifiers
------------+---------
+-----------------------------------------------------------------
  invite     | integer | not null default
nextval('public.invitecodes_invite_seq'::text)
  sponsor    | bigint  | not null
  generated  | integer | not null default ((now())::abstime)::integer
  expires    | integer | not null
  acceptedby | bigint  |
  acceptedon | integer |
  expiredon  | integer |


gr-test=> select expires from invitecodes;
   expires
------------
  1111611373
  1111551093
  1112139900
  1112169368
(4 rows)


gr-test=> select expires from invitecodes where expires <
((now())::abstime)::int4;
ERROR:  unsupported type: 23


gr-test=> select expires from invitecodes where expires > 1;
   expires
------------
  1111611373
  1111551093
  1112139900
  1112169368
(4 rows)


gr-test=> select expires from invitecodes where 1 <
((now())::abstime)::int4;
   expires
------------
  1111611373
  1111551093
  1112139900
  1112169368
(4 rows)


I haven't a clue how to go about debugging this. Any pointers?