Error on loading personal combo style

Hello,

CKEditor 3.0
I don't know why but I can't load a personal combo style, there is a javascript error:

Line: 62
Character: 2085
Code: 0
Error message: 'length' is null or is not an object.

The init editor function is:

CKEDITOR.config.width = 600;
CKEDITOR.config.Height = 200;
CKEDITOR.config.language = 'en';
CKEDITOR.config.customConfig = '';
CKEDITOR.config.contentsCss = '../home.css';
CKEDITOR.config.stylesCombo_stylesSet = 'mystyles:http://rainey/advanto/admin/ckeditor/defaultcss.js';
CKEDITOR.replace( 'memDescripcion',
{
toolbar : [
['Source'],
['Cut','Copy','Paste','PasteText','PasteFromWord','-', 'SpellChecker'],
['Undo','Redo','-','Find','Replace','-','SelectAll','RemoveFormat'],
'/',
['Bold','Italic','Underline','Strike','-','Subscript','Superscript'],
['NumberedList','BulletedList','-','Outdent','Indent','Blockquote'],
['JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock'],
['Link','Unlink'],
['Image','Flash','Table','HorizontalRule','SpecialChar'],
['Styles'],
['Maximize', 'ShowBlocks','-','About']
]
});

and the defaultcss.js is a copy of ckeditor\plugins\stylescombo\styles\default.js

Any help would be appreciated.