The issue may be "reproduced" by downgrading linux-doc to the intrepid-updates version, and installing intrepid-updates' linux-doc-2.6.27, (removing linux-doc-2.6.28), and then running "update-manager --dist-upgrade".
The GUI reports that there are no available updates. /var/log/dist-upgrade/apt.log show relevant apt messages.
The issue may be "reproduced" by downgrading linux-doc to the intrepid-updates version, and installing intrepid-updates' linux-doc-2.6.27, (removing linux-doc-2.6.28), and then running "update-manager --dist-upgrade".
The GUI reports that there are no available updates. /var/log/ dist-upgrade/ apt.log show relevant apt messages.