Desktop freezes when I use the resize grip on a Gtk3 application

[Jeremy Henty]

I have already emailed the Gtk list about this but have heard nothing
from them yet.  Perhaps you can give me some help.

Gtk3 applications have a resize grip  at the bottom right.  If I click
on that grip then my desktop  instantly freezes.  When I kill the Gtk3
application everything returns to normal.  This happens on my standard
icewm desktop and  also with twm.  (I tried starting  X with no window
manager at all but then the mouse just disappears.  Not sure what I am
doing wrong there.)

There is no problem with Gtk2 applications that have a resize grip.

When the desktop  is frozen everything appears to be  idle (ie. 'S' in
the 'S' column in htop.)

I'd really appreciate any tips for how to investigate this further.

(Linux 2.6.37, Xorg 7.5, icewm 1.3.7)

Regards,

Jeremy Henty