Firefox vanished when minimised

Just done with the fresh install and this time I am using KDE.

Here's the details:-

openSUSE 12.3
Firefox 22.0
KDE 4.10.5 release 1

Minimizing firefox definitely will make it disappeared and I lost all my works when this happen, only for firefox but other applications (chrome, dolphin, etc etc) working very well.

Is there any workaround with this?

Thanks.