One of Maverick’s new features is better control for multiple displays, which includes allowing each display to show it’s own menu bar. Unfortunately having menu bars on each display may yield unexpected results, especially when running older applications.

This feature can be turned off, but it’s not in the Displays system preference pane. Instead, to prevent the menu bar from showing on anything other than the primary display, open the Mission Control system preference pane and uncheck the option for “Displays have separate Spaces”.