Third party youtube app as default on iOS 5.1.1 (iPad1,1, jailbroken)
Just install any good third party youtube app from the app store, like Jasmine or Youtube Pro etc... Or since your iPad is jailbroken install a tweak called: older version of the app (if you can't find it on cidya try google), and find a version of official youtube app by google that supports ios 5.x.x