Steps to recover:
- If you have more than one severs running in the form, go to the server in the form, where the Content editor popups are working fine.
- Go to: C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033
- Replace the HtmlEditor.js , BFORM.js and OWS.js with the healthy server's files.
While trying to edit(edit->modify shared webpart-> rich text editor) a Content Editor Webpart, Rich text editor window will popup.