i'm not really sure whats happening here but try this, open xterm and run (you need to have 'rootsh' installed) root apt-get update apt-get -f install
The following packages have been kept back: libsdl-mixer1.2 perl-base The following packages will be upgraded: avahi-daemon avahi-dnsconfd fcam-drivers libbavahi-client3 libavahi-glib1 libclutter-1.0-0 libdmtx0a libgcrypt11 libhildon-extras1 liblongcat1 poppler-utils python python-all python-cairo python-conic python-evolution python-gobject python-minimal python-osso python2.5-qt4-common python2.5-qt4-core python2.5-qt4-gui python2.5-sip4 tracker-extractor-vorbis
also try removing the battery and holding the power button down for a few seconds before replacing it if nothing works, list your recent downloads, it could be one of them