That's probably not an issue with ubuntu, but with VirtualBox. VirtualBox 2.1.4 doesn't know about Xserver 1.6. To run Jaunty within VirtualBox and to be able to choose the resolution, you've got to wait until sun releases the next version or try the Beta of VirtualBox 2.2. With VirtualBox 2.2 it's possible to compile the kernel modules. It's even possible to run Compiz inside a virtual machine ;) http://christoph-langner.de/en/2009/03/compiz-und-3d-beschleunigung-in-virtualbox/
That's probably not an issue with ubuntu, but with VirtualBox. VirtualBox 2.1.4 doesn't know about Xserver 1.6. To run Jaunty within VirtualBox and to be able to choose the resolution, you've got to wait until sun releases the next version or try the Beta of VirtualBox 2.2. With VirtualBox 2.2 it's possible to compile the kernel modules. It's even possible to run Compiz inside a virtual machine ;) http:// christoph- langner. de/en/2009/ 03/compiz- und-3d- beschleunigung- in-virtualbox/