[jQuery] $("#mydiv").sortable is not a function error

[AdrianMG]

Hi guys! I was working with jQuery 1.2.6 development and firebug didnt
report me anybug. Now I am trying to move to 1.2.6 production, but
firebug reports me 2 erros related with "$("somediv").sortable is not
a function... What can I do? :S