Just to clarify a few things first. You have the same problem but your install is pclos and not granular. You cannot log into xfce to get to synaptic to fix the problem.
Do you have an active internet connection??
If you do when the system starts choose the safe boot option. That should boot you into a console. You will still need to log in, but it will all be done in text mode. So log in with your username and hit enter, then your password then hit enter. Now type su and then the root password.
Now you should be logged into your console as yourself with superuser privileges.
apt-get install kdelibs-suite
Make sure you accept all changes and once done reboot your system as normal. You should then be able to get into kde.