How do you forcefully release grabs?

[Adam Nielsen]

Hi all,

I just found out that the keys to forcefully release keyboard/mouse grabs have 
been reintroduced (hooray!) but unfortunately the key to release active grabs 
doesn't work - nothing happens when I press it, and the grab is still in place.

I am running "setxkbmap -option grab:break_actions" xev tells me that pressing 
Alt+Ctrl+KP/ and KP* generates an XF86Ungrab and XF86ClearGrab keysym.

When I press XF86ClearGrab then any program with an active grab is terminated, 
so that much works, but the functionality I'm really after is missing - that 
of XF86Ungrab releasing the grab but leaving the program none the wiser.  When 
I press XF86Ungrab nothing happens.  Even opening a popup menu in any program 
and pressing Alt+Ctrl+KP/ has no effect, the grab is still in place.

Am I doing something wrong?  Is XF86Ungrab the correct keysym to release an 
active grab without terminating the program?

Thanks,
Adam.