This is because Config_Database
expects the config values to be serialized. The error message is saying that the Reader was unable to unserialize
the data you requested (because you seeded your database with non-serialized values). You should set the config values using:
$config->set('key', 'value')
For example:
Kohana::$config->attach(new Config_Database);
$config = Kohana::$config->load('site');
$config->set('title', 'This is a title');
Now if we look at the data in the database you should see something like the following (take note of the format of the config_value
field):
mysql> select * from config;
+------------+------------+-------------------------+
| group_name | config_key | config_value |
+------------+------------+-------------------------+
| site | title | s:15:"This is a title"; |
+------------+------------+-------------------------+
1 row in set (0.00 sec)