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- Improved cache defragmenter to both defragment at the OS level and internal files
- Improved defrag progress dialog
- Improved download status reporting in games list
- Increased background update frequency
- Improved voice quality
- Added audio recording device selection for voice chat
- Added push-to-talk support for voice chat
- Fixed apps getting stuck at Updating 0% when downloading
- Fixed possible crash when resuming from Standby mode
- Fixed Steam preventing some PC's from entering Standby mode
- Fixed overlay sometimes getting stuck up and not responding to hot-keys after server join
- Fixed uninstalled apps becoming installed when viewing their Properties page after Steam restarts
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Source: Steam