X ignores keyboard and mouse input, but shows cursor movement (etch)

[Ralph Katz <ralph.katz@rcn.com>]

A curious and rare (2 times since Etch became stable) X freeze or hang
has me wondering what to do.

Problem: X ignores keyboard and mouse input, but shows cursor movement
and running apps update normally on-screen in visible windows (gkrellm,
gaim, etc).

What happened: Viewing email message in icedove, right-click to save
image from the email, no response to mouse clicks, mouse wheel or
keyboard input, but mouse cursor movement appears normal.  icedove
continues to fetch new mail on schedule.  The identical symptoms
happened once before while composing in icedove.

Ssh from another box to examine:  Nothing unusual in /var/log.  Kill the
icedove processes.  Screen shows icedove closing, then switches to VT1
apparently from a queued earlier attempt.  Keyboard now accepts
ctrl-alt-F7 back to X, but again is frozen to all input in X!  Just as
it was before killing icedove.

>From ssh: Restarted gdm.  All is normal.  This last line in
/var/log/Xorg.0.log.old is the only thing I could find that looked
different:
FreeFontPath: FPE "/usr/share/fonts/X11/misc" refcount is 2, should be
1; fixing.

Window manager is openbox.

Has anyone experienced this behavior?  Any ideas?  (Next time I'll
remember to check .xsession-errors.)

Thanks,

Ralph Katz