I have installed Ubuntu 12.10 (x64) in VirtualBox 4.2.4 on Windows 7, and installed Guest additions with no problems reported. I set the display memory to 128Mb. After rebooting, the display settings only show 4x3 aspect ratio with a max of 1600x1200. My screen is 1920x1200.
I created a Ubuntu 11 installation in VirtualBox using the included .iso and after installation of GuestAdditions it works fine.