I had that problem too, but before then, I had to get the update to work at all, which broke in exactly the same way as the previous update. Also, my n800 ran noticeably more slowly after that update, which was very disappointing.

My n800 installed the update but failed to update the product code (just as it did last big update). I checked my sources.list, as before, and found that the update repo was incorrect, changed it manually and did an apt-get update/upgrade/dist-upgrade.

My /etc/apt/sources/list.d/hildon-application-manager.list looks like this:
deb http://catalogue.tableteer.nokia.com/certified/ diablo user
deb http://catalogue.tableteer.nokia.com/certified/ diablo user
deb http://catalogue.tableteer.nokia.com/non-certified/ diablo user
deb http://catalogue.tableteer.nokia.com/non-certified/ diablo user
deb http://catalogue.tableteer.nokia.com/updates/diablo/ ./
deb http://catalogue.tableteer.nokia.com/updates/diablo-1/ ./
deb http://catalogue.tableteer.nokia.com/updates/diablo-2/ ./

Then, because I'd deleted stuff out of MyDocs, and put links there to the internal mmc card, the document package didn't work, I had to remove the links and re-create the dirs and put some dummy files in. Finally, the packages installed and dpkg-reconfigure worked, and I was upgraded.