…it’s buggy. I tried the snapshot, but that behaves strange as well. My workaround so far is to go fullscreen. Still, customize is broken: the customization buffer shows up in the wrong buffer. I haven’t found a bug description for that yet. Also, the git interface does not work. I will install magit next, to see if that helps. Anyway: Emacs on (K) Ubuntu is in bad shape…
Update: I fixed the first two problems. Turns out, emacs-snapshot does work, I just forgot to de-install emacs23-gtk and install emacs-snapshot-gtk. Thus I still fired up the old version. Customize works as well now, after uninstalling cedet and ecb, and instead using the latest ecb and cedet from Sourceforge. The versions shipping with Kubuntu are slightly out of date and were causing the buffer problem.