Desktop stays black after upgrade/login

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http://forums.fedoraforum.org – Hi, I just upgraded from F18->F19 which apparently went fine. But now I want to login, and after this I only see "fedora" in the bottom of the screen, and a pipe as mouse cursor. Apart from this, the screen stays black, no matter which desktop I select (LXDE, XFCE, Mate, Gnome). Reboot doesn't help either. Can someone help out ? Thanks Addition: after a while there seems to be an automatic logout: the mouse cursor gets back to an arrow, with a small with block as shadow cursor, and on screen a couple of lines starting with [OK]. (HowTos)