I suppose you will be encountering this issue in development.log file. Although if you seem to have a problem this means the fckeditor.js file is not properly located. else you can also have a route specifying this route. while make sure which action lead to this issue, once you are confirmed. just add the one line after installation so that you can see changes coming through.
make sure its installed properly.
I've used YUI Editor. It has less functionalities but its more stable and beautiful. Try it out.
Go through this "blog ":http://www.thewebfellas.com/blog/2007/11/23/fckeditor-tag-helper
It has some tips to debug the problem you are facing.