title: Magento: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '100000001' for key 'UNQ_SALES_FLAT_ORDER_IN
body: <p>I have installed Magento 1.9.0.1 and I am live since 1 month.
  The first order of a Client worked without Problem. 
  But now following error message appears when the order should be processed "There was an error processing your order. Please contact us or try again later."</p>
  
  <p>Log file says:
  exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '100000001' for key 'UNQ_SALES_FLAT_ORDER_INCREMENT_ID'' in /home/www/web81/html/lib/Zend/Db/Statement/Pdo.php:228</p>
  
  <p>I have read a lot of threads and also used Google but could not find a solution.
  I am a beginner and the shop should work tomorrow again :-(
  I very much appreciate your help!</p>
  
  <p>Thanks a lot for your help &amp; best regards</p>