From the additional information that you have provided for Telerik version it is noticeable that the controls release on your side is from 2010. The initial release of IE9
was in 2011 so it is expected that there might be some issues and visual glitches with RadEditor control.
That's why I would recommend you to upgrade to the latest version of Telerik UI for ASP .NET AJAX controls Q3 2014 SP1 and validate whether these issues are still happening.
If you are still experiencing the same unwanted behavior could you please isolate the issue in a sample fully runnable project that matches your setup and customizations with detailed reproduction steps and environment details (OS, Browser, .NET version), so we will be able to reproduce and examine it locally on our side?
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