On my new created slaves I can't install any type of Addons. I will get always a blank page. The corresponding URL is test.social-link.ch/administrator/index....er&view=install.

I don't have any idea what could be the reason. Of course I did install the Components install in the first place an the master without any problems.

The problem is an all the slaves no matter how they are created (copyed from master or new installed).

It is on a new Joomla 1.7 installation.

If you have successfully installed the extension in the master and that you want to re-isntall it in a slave site, Joomla 1.6 and 1.7 provide a new functionality "discover" in the extensions / installation menu.

So try to click on the "discover" button to declare the extension in the slave site.

I did check with the "discover" button to install extensions to the slave sites.
On the slave sites witch have been created newly with Joomla installation routine, I can see and install extensions from the master.
But if I try to uninstall an extension I will get a blank page as well and the extension remains installed.

On the sites that have been created with a template as a copy from the master there are no extensions visible to install. (I did install a few one new on the master).

Is the blank page a normal behavior on Joomla 1.7 when I try to install an extension on th slave with the normal upload procedure?

Blank page is generally the symptom of a PHP fatal error somewhere.
So you have to check your "error log" file to get more info.

This may be due to a problem of permission, problem of missing files, ....

No this is not normal.
If you want that we have a look on your server, this is also possible with our billable support that you can order at
www.jms2win.com/en/joomla-multisite?page...35&category_id=1

I did install the version 1.2.64 in the meantime, but there is still the same error. The logs don't show any abnormal incidence (apache error.log). I think there is still something wrong with the patches. I will order a bit of the paid support.