Minimised windows vanish in KDE4

OpenSuse 12.3/KDE4

When KDE4 was first installed, minimised windows would appear as expected on the bottom panel that contains the system tray. Now minimised windows just vanish. Something must have happened but I don’t recall what I did. I deleted the panel and replaced it with a new (system tray) style panel, but this has not helped. Has anyone else experienced this issue or can tell me what is going on please?
Thank you

Can you find the missing windows with ALT-TAB?

Right click on the task bar, and select “Task Manager Settings”. Check those – perhaps you have a setting that is causing problems.

You need a task manager in your bottom panel.
Unlock widgets and open your bottom panel.
Click *add widgets
*Then search for *Task Manager *and install
SUSE Pastelock your widgets once finished so you don’t accidentally delete it again.

I did not know that the task manager widget even existed, let alone needed. I must have deleted it without realizing so yes, I will lock the widgets.
The puzzle is now resolved.and thank you both for your help.