Suddenly, grep, list-buffers etc. split the screen horizontally... but .emacs is unchanged!

[Tom Ritchford]

Suddenly, in the middle of a long emacs session (it had been up for
over a week) my terminal-based emacs -nw now splits horizontally for
every new window (grep, compilation, list-buffers, etc).  I've used
emacs for over 25 years and never gotten into this state.

I restarted emacs - no luck.

My .emacs hadn't changed in a while.  Just to be sure, I reverted to a
backup .emacs from February, when I'm sure this problem didn't occur -
nope!

I don't tend to make huge changes to my system.  The one thing that
happened that I have to believe is related is that I loaded and ran
the OS/X emacs (with "real" windows and menus), which I decided not to
use because of the anti-aliased text.

Strangely enough, that instance of emacs splits vertically (like every
other instance of emacs I've ever used) - but I find it hard to read.

I'm very frustrated!  I use emacs for about 50 hours a week and now my
main emacs "isn't working" (EVERY time the screen splits vertically I
get diverted from my work - and that happens many dozens of times an
hour).  I really don't want to be forced to use the damned windowed
emacs, I *like* the text terminal based emacs and have used it for
over a decade.  I've been a good boy, I have complete backups of
everything, I don't change my system and yet it's now broken.

So any help is MOST appreciated!


System Details:

Mac OS/X, 10.6.2, details on request.

Terminal emacs version:
  GNU Emacs 23.1.1 (i386-apple-darwin9.7.0, X toolkit) of 2009-08-15
on hofmann

OS/X "native" emacs version:
  GNU Emacs 23.1.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54) of
2009-08-16 on black.local