CKEditor: Uncaught TypeError: undefined is not a function causes a failure to load.

I am new to CKEditor and trying to implement it in a PHP/HTML site I am working on.

Currently when my page loads I get a javascript error on the console with the following stacktrace:
 

Uncaught TypeError: undefined is not a function filter.js:388
addNamedRules filter.js:388
CKEDITOR.htmlParser.filter.CKEDITOR.tools.createClass.proto.addRules filter.js:143
CKEDITOR.htmlDataProcessor htmldataprocessor.js:43
initComponents editor.js:391
onConfigLoaded editor.js:385
(anonymous function) editor.js:306
listenerFirer event.js:144
CKEDITOR.event.fire event.js:289
CKEDITOR.editor.fire editor_basic.js:24
CKEDITOR.event.fireOnce event.js:332
CKEDITOR.editor.fireOnce editor_basic.js:31
loadConfig editor.js:266
(anonymous function) editor.js:281
callbackWrapper scriptloader.js:185
CKEDITOR.scriptLoader.load.doCallback scriptloader.js:68
CKEDITOR.scriptLoader.load.checkLoaded scriptloader.js:84
CKEDITOR.scriptLoader.load.onLoad scriptloader.js:98
(anonymous function) scriptloader.js:134

I am using the following HTML code to generate my CKEditor instance.

 

<td><p><textarea name="eventdescription" id="eventdescription" cols="80" rows="10"><%fld_eventdescription%></textarea></p> <span class="reqfield">*</span></td>

<script>
// Replace the <textarea id="eventdescription"> with an CKEditor
// instance, using default configurations.
CKEDITOR.replace( 'eventdescription', {
	uiColor: '#14B8C4',
	toolbar: [
		[ 'Bold', 'Italic', '-', 'NumberedList', 'BulletedList', '-', 'Link', 'Unlink' ],
		[ 'FontSize', 'TextColor' ]
	]
});
</script>

I have tried several version of CKEditor including the latest development release, nightly builds and a few older versions of CKEditor 3.X, all give the same error. I get this error regardless of whether or not I try to load CKEditor via class name or through CKEDITOR.replace().