Elsewhere in this thread, Steve proposed trying --use-union-type.  I
did - no joy.  I still see the same hang when attempting to delete a
large (262,500 byte) chunk of text.  Here's my config:
uname -a: SunOS ise3 5.5.1 Generic_103640-22 sun4u sparc
/u/shelton/new/src/xemacs-21.4-2001-11-05-union/configure 
'--prefix=/u/shelton/new/SunOS-5.5/xemacs-21.4-2001-11-05-union'
'--with-gcc' '--site-includes=/u/shelton/new/SunOS-5.5/include'
'--site-libraries=/u/shelton/new/SunOS-5.5/lib'
'--infopath=/u/shelton/new/info' '--with-mule=no' '--compiler=gcc'
'--cflags=-O2 -pipe -ffast-math -fno-exceptions' '--with-dialogs=no'
'--with-widgets=no'
'--package-path=/u/shelton/new/site-packages::/u/shelton/new/xemacs-packages'
'--use-union-type'
XEmacs 21.4.5 "Civil Service" configured for `sparc-sun-solaris2.5.1'.
Compilation / Installation:
  Source code location:              /u/shelton/new/src/xemacs-21.4-2001-11-05-union
  Installation prefix:              
/u/shelton/new/SunOS-5.5/xemacs-21.4-2001-11-05-union
  Additional header files:           /u/shelton/new/SunOS-5.5/include
  Additional libraries:              /u/shelton/new/SunOS-5.5/lib
  Runtime library search path:      
/u/shelton/new/SunOS-5.5/lib:/usr/dt/lib:/usr/openwin/lib
  Operating system description file: `s/sol2.h'
  Machine description file:          `m/sparc.h'
  Compiler:                          gcc -O2 -pipe -ffast-math -fno-exceptions
  Relocating allocator for buffers:  yes
  GNU version of malloc:             yes
Window System:
  Compiling in support for the X window system:
    - X Windows headers location:                 /usr/dt/include /usr/openwin/include
    - X Windows libraries location:               /usr/dt/lib /usr/openwin/lib
    - Handling WM_COMMAND properly.
  Using Lucid menubars.
  Using Lucid scrollbars.
TTY:
Images:
  Compiling in support for GIF  images (builtin).
  Compiling in support for XPM  images.
  Compiling in support for PNG  images.
Sound:
Databases:
  Compiling in support for DBM.
Internationalization:
Mail:
  Compiling in support for "dot-locking" mail spool file locking method.
Other Features:
  Compiling in support for ToolTalk.
  Compiling in support for dynamic shared object modules.
  Using the union type for Lisp_Objects.
-- 
In a minute there is time
For decisions and revisions which a minute will reverse.         T.S. Eliot
[URL: 
http://www.cs.amherst.edu/~ccm/prufrock.html]