I don't see how this is simply a problem of the window not being completely on the screen. For one, when a window happens to open in the middle instead of top-left, it is missing the window border and cannot be dragged anywhere.
Windows cannot be resized. If it was just slightly off-screen, you could still resize it via its bottom right corner. I had to move the top panel to the bottom to stop application menus from overlapping the top panel. When you fullscreen (f11) Firefox it takes the same amount of space, only about 1/3 the desktop when the VBox is maximized, suggesting it doesn't know the current screen size.
In the screenshot, I opened the Networking dialog while the VBox window was maximized. It centers. I then restored the VBox window, opened Firefox, and put it in (F11) full screen mode. Nothing is dragable or sizable. The Minimize on Firefox's full screen doesn't even work. This is not an off-the-screen issue. It might have been for one guy, but not for the rest of us.
This is VBox 3.0.2. Since installing Centos 5 yesterday, I haven't had any problems with it, yet. Only Ubuntu has this and other issues (runaway CPU; mouse coordinates quit working - had to restore snapshot to undo this problem.)
ubuntu-8.10-desktop-i386.iso
