title: Virtualbox freezes entire Ubuntu 16.04.3 LTS
body: <p>From yesterday I can't boot the Windows 7 through virtualbox running on Ubuntu 16.04.3 LTS. The entire computer would be frozen right after I double click the Windows 7 icon. I had to manually force reboot the computer every time I boot the virtualbox (ctrl+alt+F1/* doesn't help). I have tried:</p>
  
  <p>a) remove and reinstall virtualbox;</p>
  
  <p>b) delete Windows 7 but can't reinstall the windows due to computer freezing.</p>
  
  <p>Here are some session information:</p>
  
  <pre><code>$lsb_release
  Distributor ID: Ubuntu
  Description:    Ubuntu 16.04.3 LTS
  Release:    16.04
  
  $vboxmanage --version
  5.0.40_Ubuntur115130
  
  $ sudo VBoxManage list extpacks
  Extension Packs: 1
  Pack no. 0:   VNC
  Version:      5.0.40
  Revision:     115130
  Edition:      
  Description:  VNC plugin module
  VRDE Module:  VBoxVNC
  Usable:       true 
  Why unusable:
  </code></pre>
  
  <p>Any suggestions for the solution?</p>