bug#3251: 23.0.93; Gnome tooltip flashing

i Just built GNU Emacs from the BZR repository http://bzr.notengoamigos.org/emacs/trunk/
on Ubuntu 9.04 (2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009 i686 GNU/Linux).

Under Gnome, whenever I mouse over a toolbar button, or a mode line, the tooltip is displayed
but is repeatedly displayed causing very noticible screen flashing.  It doesn't happen every 
time, and will sometimes start if the mouse cursor is left hovering over a toolbar button
(not moving; the mouse not touched or moved).  

Obviously, this isn't a critical editor failure, but it is a disconcerting display effect.

In GNU Emacs 23.0.93.1 (i686-pc-linux-gnu, GTK+ Version 2.16.1)
 of 2009-05-09 on michael-portable
Windowing system distributor `The X.Org Foundation', version 11.0.10600000
configured using `configure  '--with-libotf' '--with-m17n-flt''

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: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> 
<send-emacs-bug-report>

Recent messages:
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