$.cookie is not a function

[eluser]maria clara[/eluser]
help..unable to figure the problem..this error came out when i change
$('.listFlex').flexigrid to $('.listFlex').jqgrid

$.cookie is not a function
if ($.cookie('closeNav'))\r\nar_salesorder (line 43)

$.cookie is not a function
var np = $.cookie(mod+'page');\r\njs (line 177)

$.cookie is not a function
var cNavs = $.cookie('Navs');\r\n

thanks,
maria :'C