SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '10-0-1-19' for key 1

This issue was discrovered in 1.4.0.1 release
Please check Magento Forum for more detailed information:
http://www.magentocommerce.com/boards/viewthread/77031/

However, changes made are saved correctly.

We suggest to ignore this warning till it'd be fixed in further Magento releases.

Or you can try this workaroung:
You just have to remove
/app/design/frontend/default/your theme/template/catalog/product/list/toolbar.phtml
and replace it by
app/design/frontend/base/default/template/catalog/product/list/toolbar.phtml

From old cart
To new cart