Initially I had the Samsung Unified driver installed from files given by Samsung itself, but this caused trouble due to the changing of various permissions within many of the system files. Then I installed a version of Samsung's software that was developed by someone at http://www.bchemnet.com. This worked for a while.

But, recently I started getting the error "/usr/lib/cups/filter/rastertosamsungsplc failed". I then removed all the samsungmfp stuff I had installed (IE, the Samsung Unified Driver stuff from http://www.bchemnet.com) and installed and used the package hannah-foo2zjs to download the firmware for CLP-300 (good to install the package foo2zjs as well). I then went to http://localhost:631 and when installing the printer I searched the ppd files and found /usr/share/ppd/foo2zjs/Samsung-CLP-300.ppd.gz. I had to look for this because the default choice was incorrect. After selecting it and setting up the printer, everything worked well.