Ardour 2.8.4 gui works slow


I use a ppa build of ardour 2.8.4 with ubuntu studio 9.10 karmic. All sound work perfectly and I think ardour is getting to be a serious alternative for home musicians and small studios. The problem is the gui side of things work slow. The lag happens when I scroll down or left-right the screen with either mouse wheel or click-dragging. Gui in other jack apps seems quite fast. My system is as follows:

AMD Athlon 64 X2 5600+
4gb of 800mhz ram
ATI x1950xt with open source radeon driver (2d works quite fast in other apps)

gnome 2.28
gtkmm 2.4-1

sorry the gtkmm version is 2.18.2-1

I assume that it is due to some issue with your graphic card.
I have exactly the same OS, processor and RAM, but a nVidia GeForce 6100 (so a pretty old and slow graphic card), and Ardour GUI works fast and smoothly.