Scrolling in GtkTreeView: very slow

[pardal-sp <pardal-sp ig com br>]

Hello, my name is Samuel, from Sao Paulo, Brazil (my English is very bad!). 
My doubt is: 
Why scrolling in GtkTreeView is so slow??? 
My machine is a Via C3 800 MHz, with 256 MB of memory. My system is Debian 
Unstable, running IceWm. 
I load 3,000 lines in a GtkListStore and show them in a GtkTreeView. I set 
the "fixed-height-mode" property of the GtkTreeView to TRUE, and the list is 
showed fast. 
But, the problem is when I scroll the GtkTreeView. 
With mouse or keyboard, the scrolling is VERY slow, and eats a lot of 
processor! 
Is there any solution for this problem? 

Thanks, 

Samuel