getting TypeError: $(...).select2 is not a function while using select2 in firefox

[sai....@gmail.com]

Hi

I am using select2 in one my projects. It is awesome plugin and works flawlessly in chrome and IE but I have problem using it in firefox.
I am using firefox 23.0.1.

Error in console:
[22:40:05.663] TypeError: $(...).select2 is not a function @

code :
script:

$(document).ready(function() {
$("#combobox").select2();
});

html:
<select id="combobox" class="inline">

I have given all necessary javascripts in my code(It is working fine in other browsers)