Gnome GUI: status line issue

[Miroslav Skoric <skoric@eunet.rs>]

Hi,

I am not sure now how that has happened, but probably somewhere during 
the system upgrade from squeeze to wheezy (the upgrade done from within 
GUI), one of my machines somehow lost the ability of the status line in 
Gnome GUI to show icons of active program windows, either normal or 
[minimized]. What to do to recover that ability? (Now in the status 
line, there are only four boxes on the right for Workspaces 1-4. All the 
remaining of the line is empty black.)