VirtualBox 4.1.22 is the latest maintenance release or VirtualBox 4.1.
There are following changes:
VMM: fixed a potential host crash triggered by shutting down a VM when another VM was running (only affected 32-bit hosts and 64-bit OS X hosts, 4.1 regression, bug #9897)
VMM: fixed a potential host crash under a high guest memory pressure (seen with Windows 8 guests)
VMM: respect RAM preallocation while restoring saved state.
VMM: fixed handling of task gates if VT-x/AMD-V is disabled
Storage: fixed audio CD passthrough for certain media players
USB: don’t crash if a USB device is plugged or unplugged when saving or loading the VM state (SMP guests only)
RTC: fixed a potential corruption of CMOS bank 1
Mac OS X hosts: installer fixes for Leopard (4.1.20 regression)
Windows Additions: fixed memory leak in VBoxTray (bug #10808)
After upgrade my 4.1.20 to 4.1.22, no automatic upgrade from 4.1.22 to 4.2. You have to download the 4.2 manually and install it.
VirtualBox 4.2.0 is released on 2012-09-13. It is a major update, with following new features.
Improved Windows 8 support, in particular many 3D-related fixes
GUI: VM groups (bug #288)
GUI: expert mode for wizards
GUI: allow to alter some settings during runtime
Support for up to 36 network cards, in combination with an ICH9 chipset configuration (bug #8805)
Resource control: added support for limiting network IO bandwidth; see the manual for more information (bug #3653)
Added possibility to start VMs during system boot on Linux, OS X and Solaris; see the manual for more information (bug #950)
Added experimental support for Drag’n’drop from the host to Linux guests. Support for more guests and for guest-to-host is planned. (bug #81)
Added support for parallel port passthrough on Windows hosts
Enhanced API for controlling the guest; please see the SDK reference and API documentation for more information
If you need VirtualBox Oracle VM VirtualBox Extension Pack, you can download it from the official site. It supports for USB 2.0 devices, VirtualBox RDP and PXE boot for Intel cards.
When you download the extension pack, be sure to download the correct one for your VirtualBox version.