As DNN supports DDRMenu since DNN 4.5, we updated our DNN 5 skins to use DDRMenu.
Make sure you have at least version 02.00.00 of DDRMenu installed.
If not, you can download it from http://dnnddrmenu.codeplex.com/releases/view/63831.
Also, review your jQuery version to use at least the jQuery 1.8.3.
For more info see http://support.bind.pt/hc/en-us/articles/204448349-jQuery-conflict-issues-in-DNN (DNN5 users section).