Installation of 64 bit Ubuntu 13.04 to VirtualBox 4.2.12 on Mac OS X 10.8.3

VirtualBox Guest Additions break desktop issue

With Ubuntu 12.10 and VirtualBox 4.2.12 the problem will be reproduced.

Try replace VirtualBox 4.2.12 with 4.2.10 for Ubuntu 12.10.

With Ubuntu 13.04 and VirtualBox 4.2.12 the problem will not be reproduced.

Guest Additions is still strongly recommended to install.

Solve the "no sound" issue

Machine settings
System/motherboard - Select ICH9 chipset
Audio - Select CoreAudio, then ICH AC97