A Steam client update is now available. To apply the update, click the File menu inside of Steam and then select "Check for Steam Client Updates...". The specific changes include:
Steam Client
Fixed voice chat in Left 4 Dead lobbies
Improved overlay screen size detection for D3D9 games with multiple swap chains with different size back buffers
Fixed rare bug with retail installer which could significantly lengthen install time
Fixed a crash on activation of a Left 4 Dead 2 4-pack gift
Update Windows 7 video driver version detection
Fix urls in chat windows sometimes not being clickable
Fixed a case where incorrect achievement or avatar images are displayed