Comment 18 for bug 205079

Addition to previous post: I checked term.log _before_ I clicked close, it was zero length then as well.

Richard's workaround worked fine.
Even after closing the update-manager, warnings about packages not installed due to failed dependencies kept coming up until I killed the corresponding python processes. Then everything worked fine, except for the -386 kernel waiting for the root filesystem indefinitely. -generic worked, and this is probably unrelated.
So, here's a short wrap-up of the workaround process, starting from when you get the offending message (preceding # means no shell input):

#close the error window; click the close button on the update-manager window and confirm. more error windows might pop up
ps ax #show all processes
#there will be one or more "python /tmp/*"-like processes. kill all of them.
cd /var/cache/apt/archives
sudo dpkg -i libgcc1_* libc6_*
sudo dpkg -i debconf* liblocale-gettext-perl_* perl-base_*
apt-get -f install
kdesu "adept_manager --dist-upgrade-devel"
# wait for it to finish, reboot when requested, wait for fsck and automatic second reboot, enjoy 8.04!
# if needed choose "generic" kernel