[jQuery] $.Event is not a function js/jquery/ui.core.js Line 345

[jQuery] $.Event is not a function js/jquery/ui.core.js Line 345

Hi all,
I'm having the following error when  opening a dialog
$.Event is not a function js/jquery/ui.core.js Line 345
I don't really understand what's happening since i'm using this code to load dialog in many places in my application an it's the first time that i'm having this problem...
If any one has an idea, it's more than welcome :)
Thank you in advance.