I'm just testing 10.04.4 -> 12.04.1 upgrades and the upgrade did complete successfully but twice during the upgrade I was presented with a dialog box that's totally unreadable, and the upgrade process does not proceed until I click on the unreadable widget in the lower right hand corner of the box. I'm attaching a screenshot.
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.9
ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24
Uname: Linux 3.2.0-29-generic i686
Date: Sun Aug 19 00:30:02 2012
com.ubuntu.update-manager first-run false
com.ubuntu.update-manager launch-time 1345345338
InstallationMedia: Ubuntu 10.04.4 LTS "Lucid Lynx" - Release i386 (20120214.2)
PATH=(custom, no user)
UpgradeStatus: Upgraded to precise on 2012-08-19 (0 days ago)
VarLogDistupgradeAptclonesystemstate.tar.gz: Error: [Errno 13] Permission denied: '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'