expat-2.0.0 (/usr/lib/libexpat.so.1) is out but KDE (and possibly some other packages) are still linking against expat-1.x (/usr/lib/libexpat.so.0). As a result they all break and refuse to execute.
This is a quick (and incomplete) list of packages on my system linking against libexpat.so.0:
airsnort 0.2.7e-1
amarok-base 1.4.2-1
avahi 0.6.12-2
bmp 0.9.7.1-4
conky 1.4.2-3
cssed 0.4.0-1
dbus 0.62-2
dia 0.95-2
digikam 0.8.2-1
ettercap NG_0.7.3-3
fbida 2.03-3
filelight 1.0rc1-1
fontconfig 2.3.95-1
fwbuilder 2.0.12-2
gaim 1.5.0-5
gd 2.0.33-2
gimp 2.2.13-2
gimp-ufraw 0.9.1-1
gkrellm 2.2.9-1
glurp 0.11.6-2
gnokii 0.6.12-1
gnuplot 4.0.0-4
graphviz 2.8-2
gtk2 2.10.2-1
gtkmm 2.10.1-1
gtkpod 0.99.4-1
gwenview 1.3.1-1
hugin 0.6.1-1
imagemagick 6.2.9.2-1
inkscape 0.44.1-1
k3b 0.12.17-1
kaffeine 0.8.2-1
kdeaccessibility 3.5.4-1
kdeaddons 3.5.4-1
kdeadmin 3.5.4-1
kdeartwork 3.5.4-1
kdebase 3.5.4-6
kdebindings 3.5.4-1
kdebluetooth 1.0_beta1-7
kdeedu 3.5.4-1
kdegames 3.5.4-1
kdegraphics 3.5.4-1
kdelibs 3.5.4-1
kdemultimedia 3.5.4-2
kdenetwork 3.5.4-1
kdepim 3.5.4-2
kdesdk 3.5.4-1
kdetoys 3.5.4-1
kdeutils 3.5.4-1
kdevelop 3.3.4-1
kdewebdev 3.5.4-1
kftpgrabber 0.6.0-1
kile 1.9.2-1
kiosktool 1.0-2
kismet 2006_04_R1-2
kkbswitch 1.4.3-1
kmldonkey 0.10.1-2
koffice 1.5.2-1
krename 3.0.12-1
krusader 1.70.1-1
kst 1.1.1-1
ktorrent 2.0.2-1
kvirc 3.2.0-1
librsvg 2.14.4-2
linuxdcpp-cvs 20060824-1
mjpegtools 1.8.0-2
mplayer 1.0pre8-1
nessus-core 2.2.8-1
nmap 4.11-1
openbox 3.3.1-1
openexr 1.2.2-5
pango 1.14.2-1
pinentry 0.7.2-3
poppler 0.5.3-2
pyqt 3.16-1
rosegarden 4.1.2.4-1
skype 1.2.0.18-2
valknut 0.3.7-2
vte 0.12.2-1
wireshark 0.99.3a-1
xine-ui 0.99.4-3
xorg-apps 1.0.2-2
xorg-utils 1.0.1-1
xscreensaver 5.00-1
yakuake 2.7.5-2