title: IntelliJ Startup Error "Cannot Lock System Folders"
body: <p>I installed <a href="https://www.jetbrains.com/idea/download/" rel="nofollow"><code>IntelliJ IDEA 15.0.1 Community Edition</code></a> but when I run the application, it displays me the following error message:</p>
  
  <pre><code>Internal error. Please report to http://jb.gg/ide/critical-startup-errors
  
  java.lang.IllegalStateException: failed to create a child event loop
      at io.netty.util.concurrent.MultithreadEventExecutorGroup.&lt;init&gt;(MultithreadEventExecutorGroup.java:81)
      at io.netty.channel.MultithreadEventLoopGroup.&lt;init&gt;(MultithreadEventLoopGroup.java:50)
      at io.netty.channel.nio.NioEventLoopGroup.&lt;init&gt;(NioEventLoopGroup.java:72)
      at io.netty.channel.nio.NioEventLoopGroup.&lt;init&gt;(NioEventLoopGroup.java:58)
      at org.jetbrains.io.BuiltInServer.start(BuiltInServer.java:78)
      at com.intellij.idea.SocketLock$2.call(SocketLock.java:131)
      at com.intellij.idea.SocketLock$2.call(SocketLock.java:112)
      at com.intellij.idea.SocketLock.underLocks(SocketLock.java:155)
      at com.intellij.idea.SocketLock.lock(SocketLock.java:112)
      at com.intellij.idea.StartupUtil.lockSystemFolders(StartupUtil.java:263)
      at com.intellij.idea.StartupUtil.prepareAndStart(StartupUtil.java:101)
      at com.intellij.idea.MainImpl.start(MainImpl.java:34)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:497)
      at com.intellij.ide.plugins.PluginManager$2.run(PluginManager.java:90)
      at java.lang.Thread.run(Thread.java:745)
  Caused by: io.netty.channel.ChannelException: failed to open a new selector
      at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:127)
      at io.netty.channel.nio.NioEventLoop.&lt;init&gt;(NioEventLoop.java:119)
      at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:97)
      at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:31)
      at io.netty.util.concurrent.MultithreadEventExecutorGroup.&lt;init&gt;(MultithreadEventExecutorGroup.java:77)
      ... 17 more
  Caused by: java.io.IOException: Unable to establish loopback connection
      at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:101)
      at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:68)
      at java.security.AccessController.doPrivileged(Native Method)
      at sun.nio.ch.PipeImpl.&lt;init&gt;(PipeImpl.java:170)
      at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50)
      at java.nio.channels.Pipe.open(Pipe.java:155)
      at sun.nio.ch.WindowsSelectorImpl.&lt;init&gt;(WindowsSelectorImpl.java:127)
      at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44)
      at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:125)
      ... 21 more
  Caused by: java.io.IOException: An existing connection was forcibly closed by the remote host
      at sun.nio.ch.SocketDispatcher.read0(Native Method)
      at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
      at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
      at sun.nio.ch.IOUtil.read(IOUtil.java:197)
      at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380)
      at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:139)
      at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
      ... 29 more
  </code></pre>
  
  <p>The IDE doesn't boot up afterwards. It always worked flawlessly before but recently I have been getting this same error when trying to compile a <code>Java</code> project with <code>IDEA version 14.5</code>. After a clean installation of <code>15.0.1</code> it still doesn't work. It becomes quite obvious that the problem must be due to something I installed in the meantime but what could affect IntelliJ IDEA in such a way? I'm on Windows 10 and using <a href="https://www.avast.com/index" rel="nofollow"><code>AVAST!</code></a>. I tried disabling my Antivirus and Firewall but it didn't help. I also submitted a bug report. Eclipse still runs and compiles Java code just fine.</p>