You need to reactivate (deactivate, then activate again) the RadEditor features on at least one site after you upgrade to a newer version. After that you need to recycle the SharePoint web application for the changes to be applied.
When you uninstall the RadEditor for MOSS, it removes a special template file from the server - \Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\CONTROLTEMPLATES\RadEditorList.ascx
In order to install this file again, you need to activate the editor features on any SharePoint site. Only one activation is required, since the same template file is used on all sites.
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