White space between pages (Print Layout view only)You can accidentally double-click between the pages in Print Layout view and change this setting. You can change it back in Options or double-click again on the line between the pages.
When this setting is unchecked, the page display in Print Layout View appears to delete the Header section.
Make sure you are in Print Layout view, then go to Word's options:
Word 2002 / 2003: Go to Tools / Options / View Tab.
Word 2007: Go to Office button / Word Options / Display and check "Show white space between pages in Print Layout view."
Alt + Ctrl + P switches to Print Layout view
Alt + Ctrl + N switches to Normal view