In case where RadEditor is initially hidden and displayed using AJAX is causing the editor to render with incorrect width on the first show. This scenario applies for RadGrid edit template, RadEditor inside a RadPageView, etc.
This problem occurs due to the fact that RadEditor CSS files are not fully loaded when the editor calculates its’ toolbar size.
To avoid this problem you need to register the RadEditor’s CSS files manually on the page:
Since Q2 2011 you need to use the Telerik.Web.SkinRegistrar.GetWebResourceUrl() method:
If you are using VB you should, of course, replace the this keyword with Me as this is its VB counterpart.
If you are using an older version you can still use ClientScript.GetWebResourceUrl():