any ideas why it's happening (the first query should have show the result as well)

mysql> SELECT * FROM `categories` WHERE `id`=668;
Empty set (0.00 sec)

mysql> SELECT * FROM `categories` WHERE `id`= 668;
+-----+-----------+------+-------------+----------+
| id | parent_id | name | description | owner_id |
+-----+-----------+------+-------------+----------+
| 668 | 668 | root | root | 345 |
+-----+-----------+------+-------------+----------+
1 row in set (0.00 sec)

mysql> SELECT * FROM `categories` WHERE `id`='668';
+-----+-----------+------+-------------+----------+
| id | parent_id | name | description | owner_id |
+-----+-----------+------+-------------+----------+
| 668 | 668 | root | root | 345 |
+-----+-----------+------+-------------+----------+
1 row in set (0.00 sec)

now I tried again and it worked

mysql> SELECT * FROM `categories` WHERE `id`=668;
+-----+-----------+------+-------------+----------+
| id | parent_id | name | description | owner_id |
+-----+-----------+------+-------------+----------+
| 668 | 668 | root | root | 345 |
+-----+-----------+------+-------------+----------+
1 row in set (0.00 sec)

but I've tried several times before...
ideas?