Hi,
So it is failing to load the file from the wrong location:
"http://www.mynewco.eu/portale/ClientScript/tiny_mce3392/"
but that is a very old version of TinyMCE and it does not seem to exist in your installation and we ship a newer version configured in mojoPortal 2.3.9.7 Web.config like this:
<add key="TinyMCE:BasePath" value="~/ClientScript/tiny_mce357/" />
My guess is that you have something in user.config that points it to an older version or you did not use the web.config file that shipped with version 2.3.9.7
You need to look in user.config for this setting and if you find it remove it from there so it can take the value from web.config
or if you don't find it in user.config then look and see what you have for this setting in web.config and fix it.
Hope that helps,
Joe