Apple released on August 17, 2011 a new update for OS X Lion. The OS X Lion v10.7.1 Update is recommended for all users running OS X Lion and includes general operating system fixes that enhance the stability and compatibility of your Mac.
This update include fixes for:
- Address an issue that may cause the system to become unresponsive when playing a video in Safari.
- Resolve an issue that may cause system audio to stop working when using HDMI or optical audio out.
- Improve the reliability of Wi-Fi connections.
- Resolve an issue that prevents transfer of your data, settings, and compatible applications to a new Mac running OS X Lion.
- Resolve an issue in which an admin user account could be missing after upgrading to OS X Lion.
You should back up your system before installation.
Do not interrupt the installation process once you have started to update your system. You may experience unexpected results if you have third-party system software modiﬁcations installed, or if you’ve modiﬁed the operating system through other means.
Read more on http://support.apple.com/kb/HT4764