This is a Windows-only issue.
If two copies of Graphical Analysis are launched, or if Logger Pro and then Graphical Analysis are launched, the second app will not be fully functional. This can be demonstrated by choosing Manual Entry mode, when the app will look like this:
The app cannot be used in this state. Do not run two copies of Graphical Analysis, or Graphical Analysis and Logger Pro simultaneously. It is best to exist all copies of these applications, and then launch only one copy of Graphical Analysis.
The behavior described in Graphical Analysis 4 won't open my .ambl file on Windows. arises from the same root cause, but the symptoms are different.