Index: lisp/mouse.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/mouse.el,v
retrieving revision 1.326
diff -u -r1.326 mouse.el
--- lisp/mouse.el	8 Jan 2008 05:12:50 -0000	1.326
+++ lisp/mouse.el	5 Feb 2008 03:29:30 -0000
@@ -925,6 +925,11 @@
 The region will be defined with mark and point, and the overlay
 will be deleted after return.  DO-MOUSE-DRAG-REGION-POST-PROCESS
 should only be used by mouse-drag-region."
+  ;; this function defines a new region, so deactivate mark before first 
+  ;; moving point, to avoid briefly resizing the previous active region 
+  ;; if any. Such a brief resize can produce poor behaviour when 
+  ;; select-active-regions is enabled.
+  (deactivate-mark)
   (mouse-minibuffer-check start-event)
   (setq mouse-selection-click-count-buffer (current-buffer))
   (let* ((original-window (selected-window))
@@ -971,7 +976,6 @@
     (mouse-move-drag-overlay mouse-drag-overlay start-point start-point
                              click-count)
     (overlay-put mouse-drag-overlay 'window start-window)
-    (deactivate-mark)
     (let (event end end-point last-end-point)
       (track-mouse
 	(while (progn