Insert into database error with CI 1.6.1

[eluser]123XD[/eluser]
Hi,

I am just update CI from 1.54 to 1.61, and the database insertion not working,
it works for 1.54, I am using MSSQL 2005.

The view page is a simple form, and in the controller I just simply get 3 post variables and in controller i am using

Code:

$data = array
    (
      'Firstname' => $firstname, //$firstname data retrieve from form
      'Lastname' => $lastname,
      'Email' => $email
    );
    $this->db->insert('Demo', $data);

this brings me a error as followd
and the error as followed

Code:

INSERT INTO "Demo" ("Firstname", "Lastname", "Email") VALUES ('User', 'Tmp', '[email protected]')

I paste it into MSSQL 'new query' and execute it, it works. Anyone have any ideas??
I think it's the problem with the double quotes around the table name, but i don't know how to fix it.

Cheers,