virtualbox.org

I just upgraded to 1.6 since I notify that there is Seamless mode support. When I switch to seamless I just get some black squares on my desktop and that's all. I can of course switch back (fortunately) and continue without any problem.
Anybody observing the same?
My conf is:
Debian testing, 2.6.23, dual core, fwvm2, Xorg 7.3, NVidia bin driver for FX 570.
16MB video for the hosting XP.

Thanks for any hint.

I just find out, that entire screen is black, but windows itself has very strange resolution. Just a very narrow vertical bar. Wenn I switch back from seamless windows, then there is still the same narrow resolution also within VM window.