Magento 1.9 – Cannot Save Shipment

Unfortunately My Magento Backend Shows error While Ship order in

Cannot save shipment.

I don't know what is the problem recently only it happend

My exception.log

016-02-29T13:44:58+00:00 ERR (3): 
exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '100000257' for key 'UNQ_SALES_FLAT_SHIPMENT_INCREMENT_ID'' in /home/domain/public_html/lib/Zend/Db/Statement/Pdo.php:228
Stack trace:
#0 /home/domain/public_html/lib/Zend/Db/Statement/Pdo.php(228): PDOStatement->execute(Array)
#1 /home/domain/public_html/lib/Varien/Db/Statement/Pdo/Mysql.php(110): Zend_Db_Statement_Pdo->_execute(Array)
#2 /home/domain/public_html/app/code/core/Zend/Db/Statement.php(291): Varien_Db_Statement_Pdo_Mysql->_execute(Array)
#3 /home/domain/public_html/lib/Zend/Db/Adapter/Abstract.php(480): Zend_Db_Statement->execute(Array)
#4 /home/domain/public_html/lib/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('INSERT INTO `sa...', Array)
#5 /home/domain/public_html/lib/Varien/Db/Adapter/Pdo/Mysql.php(428): Zend_Db_Adapter_Pdo_Abstract->query('INSERT INTO `sa...', Array)
#6 /home/domain/public_html/lib/Zend/Db/Adapter/Abstract.php(576): Varien_Db_Adapter_Pdo_Mysql->query('INSERT INTO `sa...', Array)
#7 /home/domain/public_html/app/code/core/Mage/Core/Model/Resource/Db/Abstract.php(453): Zend_Db_Adapter_Abstract->insert('sales_flat_ship...', Array)
#8 /home/domain/public_html/app/code/core/Mage/Sales/Model/Resource/Order/Abstract.php(425): Mage_Core_Model_Resource_Db_Abstract->save(Object(Mage_Sales_Model_Order_Shipment))
#9 /home/domain/public_html/app/code/core/Mage/Core/Model/Abstract.php(318): Mage_Sales_Model_Resource_Order_Abstract->save(Object(Mage_Sales_Model_Order_Shipment))
#10 /home/domain/public_html/app/code/core/Mage/Core/Model/Resource/Transaction.php(151): Mage_Core_Model_Abstract->save()
#11 /home/domain/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/Order/ShipmentController.php(120): Mage_Core_Model_Resource_Transaction->save()
#12 /home/domain/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/Order/ShipmentController.php(220): Mage_Adminhtml_Sales_Order_ShipmentController->_saveShipment(Object(Mage_Sales_Model_Order_Shipment))
#13 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_Sales_Order_ShipmentController->saveAction()
#14 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('save')
#15 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#16 /home/domain/public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#17 /home/domain/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#18 /home/domain/public_html/index.php(83): Mage::run('', 'store')
#19 {main}

Next exception 'Zend_Db_Statement_Exception' with message 'SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '100000257' for key 'UNQ_SALES_FLAT_SHIPMENT_INCREMENT_ID', query was: INSERT INTO `sales_flat_shipment` (`store_id`, `total_qty`, `email_sent`, `order_id`, `customer_id`, `shipping_address_id`, `billing_address_id`, `increment_id`, `created_at`, `updated_at`) VALUES (?, ?, ?, ?, ?, ?, ?, ?, '2016-02-29 13:44:58', '2016-02-29 13:44:58')' in /home/domain/public_html/lib/Zend/Db/Statement/Pdo.php:235
Stack trace:
#0 /home/domain/public_html/lib/Varien/Db/Statement/Pdo/Mysql.php(110): Zend_Db_Statement_Pdo->_execute(Array)
#1 /home/domain/public_html/app/code/core/Zend/Db/Statement.php(291): Varien_Db_Statement_Pdo_Mysql->_execute(Array)
#2 /home/domain/public_html/lib/Zend/Db/Adapter/Abstract.php(480): Zend_Db_Statement->execute(Array)
#3 /home/domain/public_html/lib/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('INSERT INTO `sa...', Array)
#4 /home/domain/public_html/lib/Varien/Db/Adapter/Pdo/Mysql.php(428): Zend_Db_Adapter_Pdo_Abstract->query('INSERT INTO `sa...', Array)
#5 /home/domain/public_html/lib/Zend/Db/Adapter/Abstract.php(576): Varien_Db_Adapter_Pdo_Mysql->query('INSERT INTO `sa...', Array)
#6 /home/domain/public_html/app/code/core/Mage/Core/Model/Resource/Db/Abstract.php(453): Zend_Db_Adapter_Abstract->insert('sales_flat_ship...', Array)
#7 /home/domain/public_html/app/code/core/Mage/Sales/Model/Resource/Order/Abstract.php(425): Mage_Core_Model_Resource_Db_Abstract->save(Object(Mage_Sales_Model_Order_Shipment))
#8 /home/domain/public_html/app/code/core/Mage/Core/Model/Abstract.php(318): Mage_Sales_Model_Resource_Order_Abstract->save(Object(Mage_Sales_Model_Order_Shipment))
#9 /home/domain/public_html/app/code/core/Mage/Core/Model/Resource/Transaction.php(151): Mage_Core_Model_Abstract->save()
#10 /home/domain/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/Order/ShipmentController.php(120): Mage_Core_Model_Resource_Transaction->save()
#11 /home/domain/public_html/app/code/core/Mage/Adminhtml/controllers/Sales/Order/ShipmentController.php(220): Mage_Adminhtml_Sales_Order_ShipmentController->_saveShipment(Object(Mage_Sales_Model_Order_Shipment))
#12 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Adminhtml_Sales_Order_ShipmentController->saveAction()
#13 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('save')
#14 /home/domain/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#15 /home/domain/public_html/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#16 /home/domain/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#17 /home/domain/public_html/index.php(83): Mage::run('', 'store')
#18 {main}