Updates to the Steam Client have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

Steam Client

• Fixed high CPU use during gameplay on some Hyperthreaded systems
  
• Fixed 100% CPU load at login screen
  
• Fixed the wrong dialog being shown when an error occured changing the contact email address
  
• Fixed the Half-Life 2: Demo preloader stopping at 20%
  
• Fixed a silent crash on exit when preloader is running

News Source: Steam News