This is from my apt-term log after upgrading from natty to oneiric:
Preparing to replace x11-common 1:7.6+4ubuntu3.1 (using .../x11-common_1%3a7.6+7ubuntu6_all.deb) ...^M
Unpacking replacement x11-common ...^M
dpkg: warning: unable to delete old directory '/etc/gdm': Directory not empty^M
It's not clear to me why x11-common thinks it should remove /etc/gdm (also not clear why I have /etc/gdm since this is a Kubuntu system that's never had Ubuntu installed) or what was in there that prevented it's removal. After the upgrade, the directory is, in fact, empty, so this looks like some kind ofsequencing issue. Full term-log attached.