Why my gtk problems can not act on key press sometime?

[Magicloud Magiclouds <magicloud.magiclouds@gmail.com>]

Dear all,
        I am using Debian unstable (kernel 2.6.21) with gnome.
        And sometime, my app's windows just have no react when I key in something, but they does hung, they can react on mouse actions.
        I need to unfocus and focus the window for many times, then it may work.
        I also tried other gtk wm like xfce, and it still has this key problem. But kde and qt apps do not.

Thanks.