strange DATE() problem

Hi,

I encountered strange BUG here in mysql server
Someone see that before?

old server:
mysql> SELECT count(*) AS count_all FROM leads WHERE (imported_at
BETWEEN '2007-11-09' AND '2007-11-10');
+-----------+
| count_all |
+-----------+
| 2276 |
+-----------+
1 row in set (0.56 sec)

mysql> SELECT count(*) AS count_all FROM leads WHERE
(DATE(imported_at) BETWEEN '2007-11-09' AND '2007-11-10');
+-----------+
| count_all |
+-----------+
| 2276 |
+-----------+
1 row in set (0.80 sec)

new server:
mysql> SELECT count(*) AS count_all FROM leads WHERE (imported_at
BETWEEN '2007-11-09' AND '2007-11-10');
+-----------+
| count_all |
+-----------+
| 2276 |
+-----------+
1 row in set (0.42 sec)

mysql> SELECT count(*) AS count_all FROM leads WHERE
(DATE(imported_at) BETWEEN '2007-11-09' AND '2007-11-10');
+-----------+
| count_all |
+-----------+
| 0 |
+-----------+
1 row in set (0.39 sec)