In my case 8080 is taken by some other app. Hudson should have terminated when it found the problem rather than continuing to start the other agents.

Winstone 2010/02/18 10:39:49] - Winstone Servlet Engine v0.9.10 running: controlPort=disabled
[Winstone 2010/02/18 10:39:49] - AJP13 Listener started: port=8009
[Winstone 2010/02/18 10:39:49] - Error during HTTP listener init or shutdown
java.net.BindException: Address already in use
at java.net.PlainSocketImpl.socketBind(Native Method)
at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:359)
at java.net.ServerSocket.bind(ServerSocket.java:319)
at java.net.ServerSocket.<init>(ServerSocket.java:185)
at java.net.ServerSocket.<init>(ServerSocket.java:141)
at winstone.HttpListener.getServerSocket(HttpListener.java:102)
at winstone.HttpListener.run(HttpListener.java:116)
at java.lang.Thread.run(Thread.java:595)

[Winstone 2010/02/18 10:39:49] - HTTP Listener shutdown successfully
Feb 18, 2010 10:39:49 AM hudson.model.Hudson$4 onAttained
INFO: Started initialization
Feb 18, 2010 10:39:51 AM hudson.model.Hudson$4 onAttained
INFO: Listed all plugins
Feb 18, 2010 10:39:51 AM hudson.model.Hudson$4 onAttained
INFO: Prepared all plugins
Feb 18, 2010 10:39:51 AM hudson.model.Hudson$4 onAttained
INFO: Started all plugins
Feb 18, 2010 10:39:51 AM hudson.model.Hudson$4 onAttained
INFO: Loaded all jobs
Feb 18, 2010 10:39:52 AM hudson.model.Hudson$4 onAttained
INFO: Completed initialization
Feb 18, 2010 10:39:52 AM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 54989