Brightness up/down keys stopped working?

[David Rosenstrauch]

I'm not sure what triggered this, but it looks like some recent upgrade 
has disabled the XF86MonBrightnessUp & Down keys, and I think the issue 
might be limited to XFCE.  (When I run xev under XFCE, it never 
registers that key press.  But when I launch fluxbox in VT8 and run xev 
there it does.)

Anyone aware of any recent release that might have caused this?  (And, 
if so, how I might fix it?)

Thanks,

DR