When I cut (kill) text in Emacs 22.1.1 (in its own window on X, in KDE, on Kubuntu), I can\'t paste (yank) it in any other application.
I always use quick paste -- drag selection in emacs, hit the middle mouse button in target window.
(From the reference to kate, I take it you're on linux or similar and probably using emacs in X one way or another.)