The upgrade went fine, and my site was up and running without any problems. But after a restart of IIS I get the following error:

[FileLoadException: Could not load file or assembly 'Telerik.Web.UI, Version=2013.1.403.40, 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)]

In the web.config I found this:
<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Telerik.Web.UI" publicKeyToken="121fae78165ba3d4" />
        <!--Upgraded by DotNetNuke.Telerik.Web version 7.0.6 - Date: 6/26/2013 5:12:23 PM-->
        <!--<bindingRedirect oldVersion="2008.0.0.0-2020.0.0.0" newVersion="2012.3.1205.40" xmlns="urn:schemas-microsoft-com:asm.v1" />-->
        <bindingRedirect oldVersion="2008.0.0.0-2020.0.0.0" newVersion="2013.1.403.40" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>

I guess that states that the 7.0.6 upgrade (yesterday) changed the telerik version from 2012.3.1205.40 to 2013.1.403.40 

Please help. 

Additional info:
I'm using the non-source version, community edition.

The telerik files in my bin folder are the old version. There don't seem to be any new telerik files in the zip.
I found this ancient topic (http://www.dotnetnuke.com/Resources/Forums/forumid/-1/threadid/350999/scope/posts.aspx) where Sebastian states that "when using the source version of DNN, you need to copy over telerik from library/components/telerik/bin to /website/bin first"

I downloaded the 7.0.6 source version, only to find that the mentioned components folder is completely empty.

 

OK, copying the two telerik dlls fixed dnn from completely not starting. But now everything is broken.

My skin fails to load because of
Could Not Load Skin: /Portals/_default/Skins/inschrijfportal/onecolumn.ascx, Error: c:\sites\inschrijfportal\admin\Skins\Login.ascx.cs(84): error CS1061: 'DotNetNuke.Entities.Portals.PortalSettings' does not contain a definition for 'HideLoginControl' and no extension method 'HideLoginControl' accepting a first argument of type 'DotNetNuke.Entities.Portals.PortalSettings' could be found (are you missing a using directive or an assembly reference?)

Maybe this has something to do with hiding the login link (which is why I upgraded, this is a new security setting, and it worked just fine)

So I tried to open the site settings:
Error: Site Settings is currently unavailable. DotNetNuke.Services.Exceptions.ModuleLoadException: c:\sites\inschrijfportal\DesktopModules\Admin\Portals\SiteSettings.ascx.cs(328): error CS0117: 'DotNetNuke.Common.Globals' does not contain a definition for 'ValidateModuleInTab' --->

Hmm maybe change back to a default skin first?
Error: is currently unavailable. DotNetNuke.Services.Exceptions.ModuleLoadException: c:\sites\inschrijfportal\DesktopModules\Admin\Tabs\ManageTabs.ascx.cs(963): error CS1061: 'DotNetNuke.Entities.Modules.ModuleController' does not contain a definition for 'InitialModulePermission' and no extension method 'InitialModulePermission' accepting a first argument of type 'DotNetNuke.Entities.Modules.ModuleController' could be found (are you missing a using directive or an assembly reference?) --->


And then I noticed the update link at the dnn logo...
http://update.dotnetnuke.com/redirect...
So it thinks it's running 7.0.4 again?