"Invalid cast" warning

[Claude Jones]

I've been using smartpm to keep my machine up to date. I get the following 
warning nearly every time, on two separate FC4 boxes:

(smart:5090): GLib-GObject-WARNING **: invalid cast from `GtkTreeView' to 
`GtkRange'

There are usually about 8 or 10 of these in the logview window with different 
numbers after "smart:"
They don't seem to affect anything. I've googled this error but got no 
meaningful results. I've tried the smart and kde-redhat lists but got no 
responses. 
Does anyone know what this warning means?
-- 
Claude Jones
Bluemont, VA, USA