Hi there,
When there are enough items in the Empire Tree to make the scroll bar appear, there is a strange bug where scrolling the mouse wheel or click on the bar or arrows causes part of the Empire Tree to disappear instead of scrolling properly.
I am running Windows Vista 64 bit (on Intel Core 2 Duo), resolution is 1920 x 1200, although I have seen the problem in other resolutions as well. Graphics card = NVIDIA 8800 GT.
Thanks!