Strange scrollbar problem: lost mouse-up click

For some time now, on both of my computers (Ubuntu 8.10 and 8.04), and on both Firefox and Chrome, I've been noticing lost mouse-up events when I click on the scrollbar away from the thumb. That's supposed to scroll by one page, but what I observe occasionally instead is either - the thumb sticks

root object in Glib/Gtk etc

I'm trying to find the answer to this basic question, am I right in thinking that all Glib/Gtk objects/widgets descend from GObject ??? and that it supplies the RTI (Runtime Type Information) for the whole system ___ gtk-list mailing list gtk-list@gnom