Comment 42 for bug 43066

Craig's last path works very well for me.

For non programmers, you could add a few details :
1) after running :
apt-get source gnome-panel
apt-get build-dep gnome-panel
... you'll have a new folder named "gnome-panel-xxx" ("xxx" might change, for me it's "2.30.2").
The file that you need to modify is located in "gnome-panel-xxx/applets/wncklet/window-list.c".
2) once you're done, use your terminal to navigate to "gnome-panel-xxx" and type "dpkg-buildpackage". It might take some time to compile the whole thing.
3) when it's done, type "cd .." and "ls". You should see several ".deb" packages.
I only installed one : "gnome-panel_xxx-1ubuntu3_i386.deb" (is it necessary to re-install the others?). To install it, type : "sudo dpkg --install gnome-panel_xxx-1ubuntu3_i386.deb"
4) when it's done, type "killall wnck-applet" : a prompt (or several ones) will ask you if you want to restart the program, answer yes. The problem is now fixed !

Thank you Craig !

That said, it's sad to see that this bug is still present 4 years after its discovery.
The fix appears to be simple, and the problem is quite annoying.