KDE 4.2.1-3.FC10 - Alt key sometimes gets stuck when Alt-Tabbing

[Chris January]

Using KDE 4.2.1-3.FC10 on Fedora 10/x86_64.

Sometimes after pressing Alt-Tab to switch tasks the Alt key gets
stuck down. That is to say every X client application connected to the
X server behaves as if the Alt key is still pressed, even though it
physically isn't. If I kill kded4 from a text console the problem
disappears. If I then restart kded4 and the Alt-Tab functionality is
restored, but the problem may happen again after some time.
The problem doesn't occur every time I Alt-Tab but occurs maybe once an hour.

This problem started to occur within the last few weeks after an
update to the latest KDE from kde-testing (so probably since 4.2.1).

Regards,
Chris