Picture does not go away?

For a few days I have been seeing this image on my laptop screen continuously, I can't close it. I've restarted my laptop several times. The antivirus program doesn't find anything either. When I click on the picture it shows the "OK" button, but when I click the button nothing happens.

I thank you in advance for helpful answers.

Is this in a program or is it always displayed?

Some program seems to have no network access. I would look in the task manager and start shooting programs until the picture no longer appears. Then you know what the program is

It is always displayed

I just opened the task manager and closed all tasks, the picture is still showing.

Yes, but it must be some program that shows this message.

download the ProcessExplorer from Sysinternals. In this program there's a kind of crosshair. You drag this onto this window. The ProcessExplorer can then tell you where the message comes from.

http://live.sysinternals.com/procexp.exe