Version:            (using KDE 4.2.0)
OS:                Linux
Installed from:    SuSE RPMs

I am using several virtual desktops (on a multi screen layout, don't know if that matters) and have the following shortcuts assigned:
Win/Meta+Tab = Switch to next window
Alt+Tab = Walk through windows

When I rapidly switch between desktops and windows and use the keyboard shortcuts, the keyboard is lost, i.e. no keystrokes are recognized any more.

Kwin is still alive, and I can use the mouse. The keyboard can be brought back by issuing "kwin --replace", either by calling a script with that content, or by pasting it into a shell together with a linefeed.

I am using some composite effects with XRender for improved window management (on a radeonhd driven ATI card), but not for Window and Desktop switching (to slow, and does not add a personal benefit).

I can observe this issue on several boxes, all running either i386 or x86_64 openSUSE 11.1 with KDE 4.2 from factory repos.