I had the same problem on my up to date Kubuntu 8.04 Beta. The problem is that /etc/ati/authatieventsd.sh can't locate a file. It's got the wrong path.
In /etc/ati/authatieventsd.sh change this line:
XDM_AUTH_MASK=/var/lib/xdm/authdir/authfiles/A$1*
to:
XDM_AUTH_MASK=/var/run/xauth/A$1*
This solved the black screen hanging on logoff for me.
I'm not quite sure what to change if you're using Gnome, but I suspect it's this line:
GDM_AUTH_FILE=/var/lib/gdm/$1.Xauth
I had the same problem on my up to date Kubuntu 8.04 Beta. The problem is that /etc/ati/ authatieventsd. sh can't locate a file. It's got the wrong path.
In /etc/ati/ authatieventsd. sh change this line: AUTH_MASK= /var/lib/ xdm/authdir/ authfiles/ A$1*
XDM_
to: AUTH_MASK= /var/run/ xauth/A$ 1*
XDM_
This solved the black screen hanging on logoff for me.
I'm not quite sure what to change if you're using Gnome, but I suspect it's this line: AUTH_FILE= /var/lib/ gdm/$1. Xauth
GDM_