6 Answers, 1 is accepted

The problem is due to the fact that the RadEditor's DialogHandler and SpellCheckHandler httpHandlers are registered in the web.config file with their fully qualified names and their versions are not updated.
Check out the following KB article for more on this.
http://www.telerik.com/support/kb/aspnet-ajax/editor/error-could-not-load-file-or-assembly-telerik-web-ui-version-xxxxx-x-xxxx-x-culture-neutral-publickeytoken-xxxx-or-one-of-its-dependencies.aspx
Thanks,
Shinu.

I already done this one and still having some problems. I downloaded the latest release (Q1 2011) of radcontrols. What I did is put his handlers in my web.config.
<httpHandlers>
...
<add path="Telerik.Web.UI.DialogHandler.aspx" verb="*" type="Telerik.Web.UI.DialogHandler, Telerik.Web.UI"
validate="false" />
<add path="Telerik.Web.UI.SpellCheckHandler.axd" verb="*" type="Telerik.Web.UI.SpellCheckHandler, Telerik.Web.UI" validate="false" />
</httpHandlers>
I did not use the one below becase I don't know th Token and the version of the radcontrol. Does the two have difference?
<httpHandlers>
...
<add path="Telerik.Web.UI.DialogHandler.aspx" verb="*" type="Telerik.Web.UI.DialogHandler, Telerik.Web.UI, Version=2007.2.1107.0, Culture=neutral, PublicKeyToken=121fae78165ba3d4"
validate="false" />
<add path="Telerik.Web.UI.SpellCheckHandler.axd" verb="*" type="Telerik.Web.UI.SpellCheckHandler, Telerik.Web.UI, Version=2007.2.1107.0, Culture=neutral, PublicKeyToken=121fae78165ba3d4"
validate="false" />
</httpHandlers>
<httpHandlers>
...
<add path="Telerik.Web.UI.DialogHandler.aspx" verb="*" type="Telerik.Web.UI.DialogHandler, Telerik.Web.UI, Version=2007.2.1107.0, Culture=neutral, PublicKeyToken=121fae78165ba3d4"
validate="false" />
<add path="Telerik.Web.UI.SpellCheckHandler.axd" verb="*" type="Telerik.Web.UI.SpellCheckHandler, Telerik.Web.UI, Version=2007.2.1107.0, Culture=neutral, PublicKeyToken=121fae78165ba3d4"
validate="false" />
</httpHandlers>
Could you please make sure that there is not a reference to the old RadEditor.dll in the Reference section of you web application in Visual Studio?
If you still experience any problems, please open a support ticket and send your project that demonstrates the error. I will examine it and provide a solution.
All the best,
Rumen
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get now >>

Any idea sir?

make sure u already remove the older dll from your project and verify both all source code and web.config files, this bug occurs only when there is still leftover references in your project.
kind regards.
Kind regards,
Rumen
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get now >>