Please proceed as follows: With Emacs -Q read the attached file
hiselwin.el into a buffer, evaluate it via `eval-buffer', split your
single window frame via <C-x 2>, and do <C-end> in the upper window.
Here it does not move the cursor to the end of the buffer but to line
33, the one reading as

(with-current-buffer (window-buffer)

although the line number indicated in the mode-line reads as L48.
Hitting <down> at that position either does not move the cursor at all
or moves it to some position on line 40.

martin


In GNU Emacs 24.0.94.1 (i386-mingw-nt5.1.2600)
  of 2012-04-01 on MACHNO
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
  `configure --with-gcc (4.6) --no-opt'

Important settings:
   value of $LC_ALL: nil
   value of $LC_COLLATE: nil
   value of $LC_CTYPE: nil
   value of $LC_MESSAGES: nil
   value of $LC_MONETARY: nil
   value of $LC_NUMERIC: nil
   value of $LC_TIME: nil
   value of $LANG: ENU
   value of $XMODIFIERS: nil
   locale-coding-system: cp1252
   default enable-multibyte-characters: t