I lost almost 3 hours today to understand why QtCreator gives me this error as soon as a breakpoint has been triggered.
I fixed it in this way:
1) Start the debugger (F5)
2) “Reset to Default Layout” as fast as you can (as shown in the image below)
I guess it happens when you add some expression or register that put GDB in some strange way.
Let me know if you still have the issue even after this action.