What is the reason for positions of the toolbars vary between design-time and run-time in WinForms Menu(MainFrameBarManager)?

Positions of toolbars

The XPMenus framework persists the position of the toolbars when an application is closed in isolated storage. This persisted state is reapplied on the toolbars when the application is run the next time, effectively overriding the positional settings of the toolbars during design-time.

During development, the above default behavior is usually troublesome, and you can turn it off using the AutoLoadToolBarPositions property of the MainFrameBarManager.

You could also delete the app-specific persisted information in the isolated storage. This folder can be found in [INSTALLED DRIVE]:\Documents and Settings\[USERNAME]\Local Settings\Application Data\IsolatedStorage