In Excel & Word 2003 (and before) if I want to extend a vertical or
horizontal line, all I have to do is select one end of it and hold <Shift to
constrain it's movement horizontally or vertically while I dragged that point
with the mouse.

Now, with Excel & Word 2007, when I try to do that, the line shoots off the
page/sheet at an indeterminate angle (not quite vertical or horizontal) and I
have no control over the length. "Help" indicates that it should work the
same way as before, but it does not - It is now quite useless!

Sean