This error occurs on systems where the global setting prevents a website from setting this value. To fix
- Go to your applicationHost.config - usually located in
%windir%\system32\inetsrv\config\applicationHost.config
- somewhere around line 62 you'll find this:
<section name="handlers" overrideModeDefault="Deny" />
- Change that to this
<section name="handlers" overrideModeDefault="Allow" />
that's it :)