Hello Robert Smith,
The RadEditor dialogs receive encoded arguments such as skin and configuration information (for example the ImagesPaths, DialogCssFiles) via the URL. In addition RadEditor follows the HTTP rules, which allow up to 2000 symbols to be used for the URL length. However, if some monitoring program such as WebSense or a Proxy server decrease the URL length for example to 1700 symbols then this could break the loading of the editor dialogs and cause an error.
You should contact your network administrator. You can read more about that here
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