Need help--can not set up tax rate correctly

I just started to use cs-cart, but have problem to set up tax rate.

I edited tax rate ; default destination ( all countries) rate value=10, type=percent(%)

in general tag:


registration number: 1234242


rates depends on=shipping address


price included tax=ticked

It supposed all right

when I saved it, system says:

Database error: Incorrect integer value: '' for column 'rate_id' at row 1 (1366)

Invalid query: INSERT INTO cscart_tax_rates (rate_id, rate_value, rate_type, destination_id, tax_id) VALUES ('', '10', 'P', '1', '6')


File: C:\wamp\www\cscart\core\fn.database.php

Line: 263

Function: db_error

File: C:\wamp\www\cscart\controllers\admin\taxes.php

Line: 190

Function: db_query

File: C:\wamp\www\cscart\controllers\admin\taxes.php

Line: 63

Function: fn_update_tax

File: C:\wamp\www\cscart\core\fn.control.php

Line: 582

Function: include

File: C:\wamp\www\cscart\core\fn.control.php

Line: 436

Function: fn_run_controller

File: C:\wamp\www\cscart\admin.php

Line: 28

Function: fn_dispatch

what is the problem? It is urgent help.