Hello,
i have installed boinc 7.14.2 (x64) on a self-build-hardware with Intel I7 and Asus Mainboard.
It worked very good till yesterday. After a reboot the Software is not working anymore. When i start the Manager there comes:
"Ermittle den aktuellen Status" (Get the current status)
and then:
"Verbindung mit dem Basisclient nicht möglich." (Cannot connect to the base client)
And that was it.

I just reinstalled the boinc client and after the reboot i can see the PC is still working on some rosetta-tasks, but i can´t see anything of them in a window.

Ok, just now i fixed it.
I write the answer here, perhaps someone else can use it to.

I read in another thread to press "File" "Select computer" and enter there the name of the PC.
Problem with that: in the Simple View there is no "select computer" button visible.

So if you have the same problem: click on "view" and seclect "Advanced View"
--> in this view you can connect the GUI to the Client again.