Largest number of bitcoins at a single address at one time? What is the largest number of bitcoins that were stored in a single address at any one time to date?

I know there were >474320 BTC at this address at 2011-07-18 (identified to be MtGox's from the 424 242.42424242 transaction). Has any address ever contained more than this?
Here's a complete list of 'record setting' address balances over time:

   date        block  transaction       balance                    address
-----------   ------  -----------   ---------------   ----------------------------------
Jan 03 2009        0   4a5e1e4b:0       50.00000000   1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa
Jan 14 2009      496   a3b0e9e7:0       61.00000000   1BBz9Z15YpELQ4QP5sEKb1SwxkcmPb5TMs
Jan 15 2009      586   4d6edbeb:0      250.00000000   19QKDUJtx9n7Vaga6nX1bVHdsnT4Khfyi6
Jan 19 2009     1055   8897ea9c:0      500.00000000   15oUEZFKAC8E8BTLt1s1jx4fPxumwB3ecr
Jan 22 2009     1296   59bf8acb:0      875.00000000   12higDjoCCNXSA95xZMWUdPvXNmkAduhWv
                              [36 records omitted for 12higDjoCCNXSA95xZMWUdPvXNmkAduhWv]
Jan 15 2010    34887   ffcea1e6:0    72374.36000000   12higDjoCCNXSA95xZMWUdPvXNmkAduhWv
Oct 02 2010    83231   689f1772:0   110001.00000000   1LUPDXYf9XD9Ee1AqCuM3gZCA3ZMKgTcgw
Oct 02 2010    83240   0ee1f4e6:1   120001.00000000   1NJWs6g6hQsgxqtpRxXLhZJwHYhH2P2bvx
Oct 02 2010    83243   31b00090:0   122001.00000000   1NJWs6g6hQsgxqtpRxXLhZJwHYhH2P2bvx
Jan 27 2011   104770   8f821069:0   400000.00000000   1AYtnRppWM7tWQaVLpm7TvcHKrjKxgCRvX
Jun 12 2011   130281   a09ac44c:1   432109.87654321   1KLahQtqDNAXvrjNyfvgSBtAhwco5ZxLp4
Jul 18 2011   136856,  e4762860:1   434242.43424242   1eHhgW6vquBYhwMPhQ668HPjxTtpvZGPC
                              [36 records omitted for 1eHhgW6vquBYhwMPhQ668HPjxTtpvZGPC]
Jul 18 2011   136870   b96a37e4:1   474320.43424242   1eHhgW6vquBYhwMPhQ668HPjxTtpvZGPC
Nov 16 2011   153509   29a3efd3:1   500000.00000000   1M8s2S5bgAzSSzVTeL7zruvMPLvzSkEAuv


And this shows for record setting transaction sizes:

   date        block   transaction       amount
-----------   ------   -----------   ---------------
Jan 03 2009        0     4a5e1e4b        50.00000000
Jan 14 2009      496     a3b0e9e7        61.00000000
Jan 15 2009      586     4d6edbeb       250.00000000
Jan 19 2009     1055     8897ea9c       500.00000000
Jan 26 2009     1945     5559270f      1000.00000000
Feb 09 2009     3645     cec658ac      2200.00000000
Mar 16 2009     7677     e6f00fa6      2400.00000000
Apr 20 2009    11666     eebd343e      3500.00000000
Jul 20 2009    19863     123a3968      6049.53000000
Oct 16 2009    25095     4aa98b18      9700.00000000
Oct 22 2009    25618     1aae9d58     11950.00000000
Oct 24 2009    25788     5d793270     12250.00000000
Oct 27 2009    25969     3cd9410f     13000.00000000
Nov 04 2009    26402     6029e51c     15500.00000000
Nov 19 2009    27525     f2e5fdd3     21850.00000000
Nov 19 2009    27528     67fc73c7     22500.00000000
Mar 06 2010    44006     23709241     23247.39000000
Jul 12 2010    65566     ba62e528     35000.00000000
Jul 26 2010    70527     b9d69463     46753.13000000
Jul 28 2010    70870     73ac0fdc     50000.00000000
Nov 04 2010    89583     3bc57f90     50000.01000000
Nov 06 2010    90003     70dab592     55000.00000000
Nov 08 2010    90505     1ec28eee     96999.00000000
Jan 27 2011   104770     8f821069    400000.00000000
Jun 12 2011   130281     a09ac44c    432109.88745232
Jun 23 2011   132749     3a1b9e33    442000.00000000
Nov 16 2011   153509     29a3efd3    550000.00000000


So both the biggest balance and the biggest transaction are in block 153509.

The transaction is 10% bigger than necessary due to some sub-optimal coin selection code in the default client.  It makes sure, when using a set of different coins to make up the transaction inputs, that the selected coins total at least one cent more than the transferred amount.  This is an attempt to prevent sub-cent change which would trigger transaction fees.  However, in some cases there is no need for any change at all.  In this case the 'spare change' it allocated was a 50k BTC coin.  I've since submitted a fix for this issue.  This 500k coin and its subsequent movements caused the spike in global Bitcoin transaction volume referred to in this question.

Data is accurate as of February 9th 2012.