Comment 1 for bug 277195

I don't know if it's a compiz problem (since it just is reproducible with visual effects "normal" or "extra" - with "none" AFAIK compiz is not used as window manager, but metacity).

It affects all programs, and always the space between tree views e.g. or other GTK elements - this space between the widgets seems to be the base window background, and mouse wheel clicks seem to be able to "pass through" this surface, they are passed to the Desktop somehow.
I don't know neitehr GTK nor C, so I can't help more finding where the problem is.

I attached a screenshot of synaptic - and marked all the gaps with red - the "sliders" between the left and right side/ between the upper list and lower description are NOT affected, I marked them red falsely.

But you can test it yourself with any program you want.
The Status bar at the bottom of Nautilus is affected too.

NOT affected at all (if I am right) are XUL surfaces like Firefox and Thunderbird, and QT->GTK engine programs like e.g. skype and virtualbox.