Screen of Ubuntu64 guest doesn't update when 3D acceleration option is "on"

[Yuri]

Once I enabled 3D acceleration in "Display options", Ubuntu64 guest 
screen stopped updating after guest window is covered by some other host 
window. So that areas that became invisible are filled with garbage 
until some window is closed or moved in guest and it repaints the whole 
screen.

This doesn't happen with Windows7 guest with 2D and 3D acceleration.

vbox-4.1.8 on 9.0 amd64 host

Yuri