Here is my VirtualBox Configuration set for Ubuntu 11.04 Virtual Machine.
In addition 3D acceleration must be enabled and VM should have decent video memory (>= 32MB)
After the first boot you may see this warning “It seems that you do not have the hardware required to run Unity. Please choose Ubuntu Classic at the login screen and you will be using the traditional environment.”
Just ignore this warning message and install latest version (4.0.6) of Virtualbox guest additions.
Shutdown the VM gracefully. Remove Installation ISO from the Virtual Disk Drive and Power up the VM.
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