To do this carefully, go to phpMyAdmin and browse the orders table in order by orders_id ...
Find the high orders_id ... this is probably just 1 of them, but check for others ...
Next, go to the Store Manager and change the High orders_id that you found to the next proper orders_id ...
If you have other High orders_id fix each one in the Store Manager with a proper orders_id ...
Once all these are fixed, browse the orders table in phpMyAdmin again by orders_id and see what the new High orders_id is ...
Now run, in phpMyAdmin this command with the value of the High orders_id plus 1, so if you see 12576 use 12577:
Code:
ALTER TABLE orders AUTO_INCREMENT = 12577
where 12577 is you next orders_id that would be valid ...
NOTE: backup your database before trying this ...
After this is done, you will want to make a test order to make sure all is working correctly ...
Be careful in doing this, and it would be a good idea to set the site Down for Maintenance while you fix it ...