this is an issue with the setting for the sub menus left attribute.
What version of menu writer are you using? I have usually seen this happen after editing a menu and using the Edit design button in the property inspector to launch the menu editor, as as result we removed that option from newer versions and recommend using the Edit Menu button instead, then launching the design editor from the quick insert screen.
send a link where i can see this and i can tell you how to fix it.