Could not load file or assembly Telerik.Web.UI

After patching to the latest version you may see a message like this:

Error:

Could not load file or assembly 'Telerik.Web.UI, Version=2008.3.1125.35, Culture=neutral, PublicKeyToken=121fae78165ba3d4' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

The cause of the problem:

The handlers registration line in the web.config ihas the wrong version number;
<add name="Telerik_Web_UI_WebResource_axd" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource, Telerik.Web.UI, Version=2008.3.1125.35, Culture=neutral, PublicKeyToken=121fae78165ba3d4"/>

Solution:

To solve the problem you can:

1. Change the version number to the correct version number.
2. Delete the version number so the line is now: <add name="Telerik_Web_UI_WebResource_axd" verb="*" preCondition="integratedMode" path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource, Telerik.Web.UI, Culture=neutral, PublicKeyToken=121fae78165ba3d4"/>