title: Network Link Conditioner seems to have no effect on network behavior on Lion, Mountain Lion
body: <p>The Network Link Conditioner preference pane (installed from the "<a href="https://developer.apple.com/downloads/index.action?name=for%20Xcode%20-" rel="noreferrer">Hardware IO Tools for Xcode - Late July 2012</a>" DMG on the Apple developer site) doesn't appear to have any effect when turned on. The original author of this question reported the symptoms on Mountain Lion. A later editor experienced the same symptoms and lack of expected network behavior change on Lion, with Xcode 4.5.1 installed.</p>
  
  <p>When enabled, /var/log/system.log shows:</p>
  
  <pre><code>Jan 17 17:36:14 matt-mmf-macbook [0x0-0x1d01d].com.apple.systempreferences[371]: System Preferences(371,0x10fac7000) malloc: *** auto malloc[371]: error: GC operation on unregistered thread. Thread registered implicitly. Break on auto_zone_thread_registration_error() to debug.
  Jan 17 17:36:18 matt-mmf-macbook System Preferences[371]: process command (simulate) failed
  Jan 17 17:36:18 matt-mmf-macbook [0x0-0x1d01d].com.apple.systempreferences[371]: _nlc_start_simulation: (os/kern) failure
  Jan 17 17:36:18 matt-mmf-macbook System Preferences[371]: Starting Network Link Conditioner
  </code></pre>
  
  <p>And the network connections do not exhibit the behavior specified by the selected profile.</p>
  
  <p>Has anyone successfully gotten it to work, or figured out what the error in system.log might mean? As of 2013-01-17, the "accepted/correct" answer does not work for everyone experiencing the symptoms.</p>