vim-gnome mousewheel/scrollbar strange behavior

Binary package hint: vim-gnome

8.04 x86 and amd64 under gnome, run gvim and open a file or create text that has more lines than are shown. when hovering the mouse over the up and down buttons on the scrollbar and using the mouse scroll wheel, the bar moves according to the scroll wheel but the text moves as if you had pressed the scroll button with a left mouse click. i expect it to scroll as it would if i had the mouse over the text and used the mouse scroll wheel.