A little inquiry with firebug reveals no errors when the dialog loads it just shows
------------------------------------- Loading package: Extras
------------------------------------- Loading package: NotebookCore, Notebook
If I press 'NEW' then an ftc is undefined error comes up in zimbra/js/zimbraMail/share/view/dialog/ZmChooseFolderDialog.js?v=110527004... on line 292:
var dialog = ftc._getNewDialog();