I get that error after adding:

config.extraPlugins = 'doksoft_image_embed';

to the config.js for ckeditor. The editor all not work at all unless I remove the extraPlugins line.

I extracted the files to the plugins directory as the instructions dictated.

I am using ckeditor 3.6.6 and Chrome 39.0.2171.

This is the code I use:

editor = CKEDITOR.replace( objname,
{
enterMode : Number( 1 ),
shiftEnterMode : Number( 2 ),
resize_enabled : false,
forcePasteAsPlainText: true,
height: 600,
width: 750,
extraPlugins: 'doksoft_image_embed',
removePlugins: 'elementspath'
,toolbar : [
// { name: 'document', items : [ 'Source','-','Save','NewPage','DocProps','Preview','Print','-','Templates' ] },
{ name: 'clipboard', items : [ 'Cut','Copy','Paste','PasteText','PasteFromWord','-','Undo','Redo' ] },
{ name: 'editing', items : [ 'doksoft_image_embed','Find','Replace','-','SelectAll' ] },
// { name: 'forms', items : [ 'Form', 'Checkbox', 'Radio', 'TextField', 'Textarea', 'Select', 'Button', 'ImageButton', 'HiddenField' ] },
'/',
{ name: 'basicstyles', items : [ 'Bold','Italic','Underline','Strike','Subscript','Superscript','-','RemoveFormat' ] },
// { name: 'paragraph', items : [ 'NumberedList','BulletedList','-','Outdent','Indent','-','Blockquote','CreateDiv','-','JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock','-','BidiLtr','BidiRtl' ] },
{ name: 'paragraph', items : [ 'NumberedList','BulletedList','-','Outdent','Indent','-','JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock' ] },
{ name: 'links', items : [ 'Link','Unlink','Anchor' ] },
// { name: 'insert', items : [ 'Image','Flash','Table','HorizontalRule','Smiley','SpecialChar','PageBreak' ] },
'/',
{ name: 'styles', items : [ 'Font','FontSize' ] },
{ name: 'colors', items : [ 'TextColor','BGColor' ] },
// { name: 'tools', items : [ 'Maximize', 'ShowBlocks','-','About' ] }
]
});

Please try to update the plugin from files.doksoft.com
I just updated the file here, your problem related to CKEditor v. 3 was fixed a two days ago.

That fixed it, thanks.