Alt-Tab does not work in my KDE

[H Xu <xusubsc@gmail.com>]

Hello,

I'm using Debian wheezy and the Tab switcher usually does not work on my 
KDE, although sometimes it works very well. I've googled and have no 
idea of what is going on here. Could anyone help me, please?

Thanks.

Regards,
H Xu
09/19/2011