"Something went wrong trying to install ...."

Hi all,

A few days ago i made my first AIR app. Nothing special, just a test.
I sent it to a friend to test but he could not run the thing, the AIR runtime was missing. So i made a download page with the 'badge" installer from the SDK and even an other "badge" installer I found on the net.

Now what's the problem.
On my friends pc it installs the AIR Runtime but that's all.
When trying again it return's an error: "Something went wrong trying to install this application. Please install the latest version of Adobe Air from http://www.adobe.com/go/getair and try again."
I'm getting the same error.
On other sites, links from the Adobe site (http://desktop.ebay.com/install.html or http://www.agileagenda.com/download/, idem dito!

What's happening?
What's wrong?