Main menu Qt Creator disappeared

[inger]

My main menu in Qt Creator which contains File Edit Build Debug Tools Windows and Help DropDownMenues have disappeared after selecting several modes for the screen. Now I am not able to get the menu back again. Can someone please help me? This is the menu that is visible when ou hold the mouse pointer at the top of the screen.

[ChrisW67]

Are you on Windows or Linux?
Can you still see the window title bar that (on Windows and Linux) appears above the menu bar you are saying has gone missing?
What happens if you switch to/from full screen mode with Ctrl-Alt-F11?
What happens if you exit and restart the program (Alt-F4)?
What happens if you use the keyboard shortcuts? Alt-F pop up the File menu? If on Windows try Alt-Space to get the window control menu.

[inger]

Thank you for your reply.

I'm using a Oracle VM VirtualBox with Ubuntu 11.10 . the OS for the main PC is Windows 7.

I can see the tiltle bar (Ubunntu [Running] - Oracle VM VirtualBox) in the upper left corner.
when I restart the program it is still the same result.
When I tried Alt-F the File menu popped up. Then I could use the mouse cursor for getting the other pop-up menues.
When I tried 'Ctrl-F (For getting the Full screen mode) The title bar for Ubuntu disappeared. The menu for the Ubuntu then is at the bottom of the screen, just like is it meant to.

Thank you ChrisW67, you put me in to the right track :)
When I pressed Alt + W, I saw the Full Screen was chosen. When I removed the tick for that, everything is fine again!