Comment 52 for bug 553789

I found this bug while researching my X locks up issue.
This solution does not address the hardware issue documented here, but
I want help anyone who is in a similar situation that does *NOT* have
the hardware lockup and that the noaccel=1 does not work.

In my case all you have to do is move a window and then immediately
click in another window. There may be other ways to reproduce this.

The only workaround is to restart the window manager or Xorg.

Investigating the issue I found this patch:
http://cgit.freedesktop.org/xorg/xserver/patch/?id=1884db430a5680e37e94726dff46686e2218d525
Subject: Revert "dix: use the event mask of the grab for TryClientEvents."

I am using xorg-server-1.8.0 and found the issue was introduced in
xorg-server-1.6.3. The patch fix appears in xorg-server-1.8.2 and later