Fatal error: Class 'CI_Controller' not found in ...

[eluser]JackU[/eluser]
I get the following error:
Fatal error: Class 'CI_Controller' not found in C:\Inetpub\wwwroot\asda.nu\ci\ci\core\CodeIgniter.php on line 233

When using this in my library:

$ci = & get_instance();

Why?

[eluser]Italo Domingues[/eluser]
Post your code

[eluser]InsiteFX[/eluser]
No space between the = and & signs.

Code:

$ci =& get_instance();