I cannot find where any antivirus program should be the problem.
But I have found the following situation:
My program seems to have a problem, perhaps with a file which is opened but not closed or a loop running continuosly?
The first time I start the IDE and run my program (in debug mode), it starts normally, but terminates with an error (access violation at address ...).
But I can only find the reason for the error if I can use the IDE and work on the code.
If I try to start it again, the ominous error F2039 appears immediately. Ending the Delphi IDE and restarting it, does not help.
Restarting the whole PC does help indeed, and at least once I can restart the program.
It seems to me that the problem with error F2039 is: the IDE cannot create a new executable file (Project1.exe) because the old one is still running (indefinitely?).
If I try to delete the executable (Project1.exe) in ...\Win32\Debug\ I get an error message saying the (delete) action cannot be completed because the file is open in Project.exe.
But the Task Manager in the "show fewer details" mode does NOT show this program running!
In the "Show more details" mode I can find <Project.exe> and end this task.
My conclusion is: My program still has a problem with something running indefinitely. I have to and will find the reason quite soon.
But this is tricky, because I can only make test runs as long as the executable file from the last test run is deleted manually.
And it was not easy to find out what happens really.
Thanks for the cooperation and ideas.