Word 2007 return key creates a new page

I hope this makes sense to someone.
I’m working with a document that has “pictures” in the footers of several pages created with section breaks. (The pictures were pdf docs where I selected the text then copied and pasted into the footers.) I am using Word to create a form by typing over the background “picture”. On one section where previously there was no text, when I hit the return key instead of moving down a line, the return creates a new page as though the line were to large vertically to fit on the page. There is no new section break, just the paragraph mark. When I highlight the line with the mouse it is only one small line.