Sharepoint 2007 Error in HtmlEditor.js Line:5740

Symptom:

A single user with Full Control permissions is having trouble using certain page-editing functions. And getting javascript error with HtmlEditor.js

Here is the error:

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 1.1.4322; .NET CLR 3.0.04506.648; InfoPath.2; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MS-RTC LM 8; MS-RTC LM 8)
Timestamp: Mon, 24 May 2010 16:13:42 UTC

Message: Invalid argument.
Line: 5740
Char: 2
Code: 0
URI: http://www.[TheSiteURL].com/_layouts/1033/HtmlEditor.js

Solution:

Add your site to your local intranet zone in your browser.

IE -> Tools -> Internet Options -> Security -> Local Intranet -> Sites

Thats all.