AIS: downloaded, installed, rebooted...
No go. No internet connection with Firefox, IE8...
Went to programs, add/delete, started another update from there
Rebooted
Now everything is back to normal. But I had to reboot twice, and after 1st reboot my Fritz!Protect (simple Firewall for Fritz!Box DSL) did not ask for permission for new program versions. That happened after second reboot, now everything is okay.
But it was no "smooth" transition as it would be needed for the "average noob user"!