LCA: Bringing X into a two-handed world

I've noticed that GTK won't accept clicks on buttons that aren't 
pre-lighted, which seems related to the issues with two mouse pointers in 
a GTK app.  For instance, whenever I'm using Synaptic, the whole UI is 
disabled as it enumerates the package database.  I tend to put my mouse 
cursor over the Search button early, and when the software re-enables it, 
my clicks do nothing unless I move the cursor off and back onto the 
button again.

I wonder if it's an idiosyncrasy of GTK or X in general...