Unwisely, perhaps, I attempted an upgrade from within a running desktop.
I replaced my sources.list entries for TDE with:
# Trinity desktop
deb
http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/debian
squeeze main
deb-src
http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/debian
squeeze main
deb
http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.1…
squeeze main
deb-src
http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.1…
squeeze main
aptitude update succeeded on the second attempt and then I ran aptitude
upgrade.
The first sign of trouble was that the window manager crashed as the update
was applied. I was left with only the running windows and no borders. The
only way to switch windows was to click in a different window, so I shut them
all down with CTRL-Q and then I selected "end current session from a
right-click menu. This dropped me straight back to a command line. All
attempts to restart X and KDM failed, so I rebooted to see if that made any
difference.
I was still stuck at the command line, so I reverted my sources.list and tried
to revert kdm. That failed with dependency issues, so I wiped all of trinity
3.5.13 and reinstalled 3.5.12, which restored my desktop to normal
functioning.
Neil Youngman