another situation which cause Fatal error: Call to a member function on a non-object

[eluser]EugeneS[/eluser]
tried to find the solution but i cant so here is description of the problem:

my home PC: php 5.x Apache 2.x windows
my work PC: php 5.x Apache 2.x windows

at work i run this code without any problems:

Code:

class Cart extends Controller {
    function Cart()
    {
        parent::Controller();
        ..........
        ..........
    }

    function Process()    
    {
        .........
        $this->load->library('somelibrary');
        .........
        $this->somelibrary->somemethod();

    }
}

BUT at home i receive this error:
Fatal error: Call to a member function somemethod() on a non-object in ......

this code start working at home only when i load library (or model) inside constructor but not inside any method

any ideas ? i have no idea what the problem :\ any tricks to not change php config file (probably this difference depend on php configuration ) because i do not know where my site will be installed ...

sure i can load library in constructor so this will work everywhere but i do not want to do so when i use this library only in one method.... no need to load it all the time.

the same problem with loading models.