Duplicate entry 'DatabaseConnection_oracle-class' for key 'PRIMARY'

Hi:

I don't not what it happens, not only when I enable module, by example, when I click into "clear al caches" (at admin/config/development/performance) that error appears.

Another example:
I enabled a module "Localization update" and the message error appears again.
But when I click into "admin/config/regional/translate" I get a new error:

PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'titania.locales_target' doesn't exist: SELECT COUNT(*) AS translation, t.language, s.textgroup FROM {locales_source} s INNER JOIN {locales_target} t ON s.lid = t.lid GROUP BY textgroup, language; Array ( ) in locale_translate_overview_screen() (line 782 of C:\xampp\htdocs\drupal-7.8\modules\locale\locale.admin.inc).
The website encountered an unexpected error. Please try again later.

and the table doesn't exists

Any idea?

Hi Osman.
Yes, mysql is where I have installed d7 .
I will develop a module to show a page with information obtained from oracle database.
But because this module isn't finished, I have created a block that connect to oracle database. At this moment, that block is disabled, and all error messages that I write on this post are with this block disabled. I don't understand why oracle messages appears with block disabled.

For more information, i show database configuration at settings.php:
$databases = array (
'default' =>
array (
'default' =>
array (
'database' => 'titania',
'username' => 'user',
'password' => '*******',
'host' => 'localhost',
'port' => '',
'driver' => 'mysql',
'prefix' => '',
),
),

'oracle' =>
array (
'default' =>
array (
'database' => 'XE',
'username' => '*****',
'password' => '******',
'host' => '192.168.0.8',
'port' => '',
'driver' => 'oracle',
'prefix' => '',
),
),
);

And the php block code (the block only shows at /node/1 ):
db_set_active('oracle');

$sql = 'SELECT * FROM hr.employees';
$res = db_query($sql);
$res = (array) $res->fetchAll();
foreach ($res as $row) {
$row = (array) $row;
print ($row['last_name']."-".$row['email']);

}

db_set_active();

and another sample:

When I enable a core module (Aggregator), the message error:
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'DatabaseConnection_oracle-class' for key 'PRIMARY': INSERT INTO {registry} (name, type, filename, module, weight) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4), (:db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9), (:db_insert_placeholder_10, :db_insert_placeholder_11, :db_insert_placeholder_12, :db_insert_placeholder_13, :db_insert_placeholder_14); Array ( [:db_insert_placeholder_0] => DatabaseConnection_oracle [:db_insert_placeholder_1] => class [:db_insert_placeholder_2] => includes/database.inc [:db_insert_placeholder_3] => [:db_insert_placeholder_4] => 0 [:db_insert_placeholder_5] => DatabaseStatement_oracle [:db_insert_placeholder_6] => class [:db_insert_placeholder_7] => includes/database.inc [:db_insert_placeholder_8] => [:db_insert_placeholder_9] => 0 [:db_insert_placeholder_10] => DatabaseLongIdentifierHandler_oracle [:db_insert_placeholder_11] => class [:db_insert_placeholder_12] => includes/database.inc [:db_insert_placeholder_13] => [:db_insert_placeholder_14] => 0 ) in _registry_parse_file() (line 179 of C:\xampp\htdocs\drupal-7.8\includes\registry.inc).

appears, and then, aggregator tables aren't created. When I go to admin/config/services/aggregator:

PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'titania.aggregator_feed' doesn't exist: SELECT f.fid, f.title, f.url, f.refresh, f.checked, f.link, f.description, f.hash, f.etag, f.modified, f.image, f.block, COUNT(i.iid) AS items FROM {aggregator_feed} f LEFT JOIN {aggregator_item} i ON f.fid = i.fid GROUP BY f.fid, f.title, f.url, f.refresh, f.checked, f.link, f.description, f.hash, f.etag, f.modified, f.image, f.block ORDER BY f.title; Array ( ) in aggregator_view() (line 22 of C:\xampp\htdocs\drupal-7.8\modules\aggregator\aggregator.admin.inc).
The website encountered an unexpected error. Please try again later.

Hi Oshman,
Thanks for your answer. I did a new installation and the problem persists.

If I delete oracle folder from "includes", the installation it's ok, without any
error. For install any module, I need to delete that folder, and copy again to "includes" folder. If I do that, when a enable a module and that module needs to do a table creation, it's ok. If the oracle folder(and files :D) exists at "includes", shows the error and don't create table at mysql.

I will try to using the 'db_driver', but at my module everithing is ok and shows the external data from Oracle. It's when i do normal task with drupal (enable modules, etc) when i get the error. I could try to put db_driver at drupal core, but i don't know where