I just came to post the same question. I would guess that Microsoft sent us an automatic patch or download that messed things up.

When I open a new document in Word, the page doesn't display the top or bottom margins. The cursor is at the top of the screen, and the page appears to be only 9 inches high, instead of 11". I tried every possible margin option and view option, and nothing changes it.

I don't notice anything different about Excel, though - I don't work with it a whole lot.

Edited: It looks fine in Print Preview, so the top and bottom margins are there. It also looks fine with any document I created before today.