Ibus eating cntl-space key

[Stuart McGraw]

In Emacs, the cntl-space key is important and
I use it frequently.  Because it conflicts with 
the use of cntl-space in Ibus to toggle Ibus
on/off, I remapped alt-space to that function in 
Ibus.  This worked well in Fedora-11 for several 
years and in Fedora-15 after I first installed it.  
It stopped working after an Ibus update but another 
Ibus update that arrived shortly after fixed it 
again.  After yet another Ibus update it is broken 
again. :-(

Currently (ibus-1.3.99.20110714-11), if cntl-space is 
assigned "Enable or Disable" in Ibus prefs, it works 
as expected.  However, typing cntl-space in Emacs is
not seen by Emacs (unsurprisingly -- I assume it was 
intercepted by Ibus).

When I delete cntl-space in Ibus prefs and assign 
alt-space instead, alt-space then toggles the IME 
on/off as expected and cntl-space has no effect in 
Ibus (also as expected).  However, cntl-space still 
has no effect in Emacs (unexpected!).

Terminating Ibus results in cntl-space working in 
Emacs again.

Is there some secret setting I am missing?  Should I 
report a bug?