This problem occurs because the styles of RadEditor are not loaded. Could you please register the external RadEditor skins as it is shown in this KB article: Registering an external skin of RadEditor
You can also take advantage of the recently introduced CDN
support which will allow you to load the controls skins from the Telerik CDN. Telerik CDN is hosted on the Amazon CloudFront service.
You can find more information about our CDN support here
By loading the external or CDN skins you will ensure that the editor will load its skin.
If the problem still exists, could you please provide a sample project and / or a LiveUrl replicating the problem so we can investigate it further?
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