I looked for duplicates before posting and couldn't readily find any, nor am I sure if this is the right place to post this report.  Please let me know if I need to correct in any way.

Dual monitors in vertical arrangement with "main" laptop monitor being the bottom and external VGA LCD being top.  I experience largely the same behavior shown here:

http://vimeo.com/50522936

In short, it appears as if there's a large "grid" that windows snap to on the second (top) display.  Newly created windows also are created in a restored state and are very small horizontally and vertically, sometimes both -- (Screenshot of new FF window creation on "top" display attached).

The issue does not seem to arise when monitors are in a horizontal (side-by-side) configuration from display configuration utility.

Screenshot contains display preference panel.

-aeh