This is the second beta of the upcoming 4.0 release. The following items were added/fixed since VirtualBox 4.0.0 Beta 1:

• ExtPacks: show a confirmation dialog before installing an extpack
  
• ICH9 chipset: fix Windows detection of the 82801IB host bridge
  
• Linux hosts: fixed a wrong dependency to libstdc++5 in the Oracle ExtPack for 32-bit Linux which prevented to install that package on recent Linux distributions
  
• Solaris hosts: fixed a bug which prevented to install ExtPacks at all
  
• Linux/Solaris hosts: fixed the changelog in VirtualBox.chm (4.0 Beta 1 regression)
  
• Audio/HDA: fixed issue with Ubuntu 10.10 guests and OpenSolaris guests
  
• Audio/HDA: fixed choppy sound of Windows guests
  
• GUI: fixed display of the file shortcuts on some older Window Manager on X11
  
• 3D support: fixed XPDM Windows Explorer crashes on Windows Vista/Win7 guests
  
• 3D support: fixed Direct3D 8/9 support on Windows XP guests
  
• Mouse: fixed mouse reporting which was not working for X11 guests with pre-4.0 Additions (4.0 Beta 1 regression)
  
• Settings: use forward slashes in paths to make settings files more portable between Windows & other platforms
  
• VBoxManage: show exact image format variant with VBoxManage showhdinfo
  
• VBoxHeadless: detect VBoxSVC crash and terminate the VM cleanly
  
• SATA: fixed DVD detection with Solaris guests
  
• Linux Additions: fixed compilation of the kernel modules with DKMS (4.0 Beta 1 regression)
  
• VMDK: fixed image corruption with async I/O (4.0 Beta 1 regression)
  
• VBoxManage: fixed image resizing and the associated help text
  
• OVA: fix wrong size writing for individual files greater 4GB (max. 8GB now)
  
• X11 guests: multi-monitor support for X.Org Server 1.3+