display strange when the panel is at the right or left side of the screen

[PSWZ-ZhangY]

Binary package hint: gnome-panel

The buttons representing current tasks in task manager applet are arranged incorrectly.
When there are a lot of tasks to be show on the task manager, the arrangement of the button changes
between one column and two columns. Sometimes it changes in high frequency, and the task manager bar
flickers.

The expression above maybe confusing because I'm not a English speaker, here is my description in my mother tongue :
把panel放在右侧之后，打开的程序一多， 按钮就会一会儿是一排， 一会是两排， 有时候会在一排和两排间来回切换， 速度很快， 都闪了～

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: gnome-panel 1:2.30.2-1ubuntu3
ProcVersionSignature: Ubuntu 2.6.35-27.48-generic 2.6.35.11
Uname: Linux 2.6.35-27-generic x86_64
Architecture: amd64
Date: Fri Mar 11 03:55:40 2011
GConfNonDefault:
 /apps/panel/general/applet_id_list=[fast_user_switch_screen0,trashapplet_screen0,workspace_switcher_screen0,window_list_screen0,show_desktop_button_screen0,indicator_applet_screen0,notification_area_screen0,clock_screen0,applet_1]
 /apps/panel/general/object_id_list=[browser_launcher_screen0,menu_bar_screen0,object_0]
 /apps/panel/general/toplevel_id_list=[bottom_panel_screen0,top_panel_screen0]
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
ProcEnviron:
 LANGUAGE=zh_CN:zh
 LANG=zh_CN.utf8
 SHELL=/bin/bash
SourcePackage: gnome-panel

[stm (spam1208)]

I can confirm this. It happens when the panel is at the right, not at the bottom. The layout changes between one-column and two-column layout whenever certain windows are activated or when I click on the panel. It's especially annoying because it's often not possible to click on a task button in order to activate a window.
At one time, when I had many open windows, it has caused very high CPU load, because it rapidly flickered between one and two column layout.