In DNN 6.0.x versions, you may receive an onClientCommandExecuting JavaScript error on pages with a texteditor control.   There are some extenuating circumstances regarding the module settings, one of which was met when we decided to uncheck Enable Pop-Ups in the Admin>SiteSettings>Usability Settings.

The fix is to upgrade to 6.1.x.  Here's a link to the issue in Gemini.