Since I don't know the cause and didn't find a way to debug this, here are the symptoms:
Ever since media-libs/mesa >= 9.1 went stable I had the problem, that the switch from Xfce on VT7 back to VT1 on shutdown fails. The screen goes black and does not show anything, but the system halts as normal. It is not possible to switch to VT1 by keyboard while the shutdown is still in progress when this has happened. I can't find anything in the Xorg or other log files according to this problem. Can't find anything related in Gentoo bugzilla or searching the web... The problem always disappeared by downgrading to mesa < 9.1, but that now requires other packages to be downgraded too, so I'd like to resolve this. It is an AMD64 system with an ATI Barts PRO [Radeon HD 6850] using KMS, desktop session with Xfce started by x11-misc/lightdm. Any hints on how to debug this problem would be highly appreciated. Andreas
