It's on the step "Installing the upgrades", says it's "Configuring virtuoso-opensource-6.1", and the last line in the log is "Unpacking linux-headers-3.5.0-17 (from .../linux-headers-3.5.0-17_3.5.0-17.28_all.deb) ..."

.. And the application just sits there doing nothing. Trying to abort now says "The system could be in an unstable state if you cancel the upgrade", so I'd rather not do that :/

Any idea how I can kick the upgrade into gear again?

EDIT: I closed the program, ran dpkg -configure (which failed). Booted ran configure again, some configuration, and things are up and running again. I'm leaving this open as I have no idea what the root cause was.