Bug in Fixpack 6.1.0.19 for WebSphere Application Server

After installing the fixpack 6.1.0.19 a NullPointerException occurs in some applications.
This is a know bug (PK72336).
This Bug causes:

[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R Exception in thread "WebContainer : 3" java.lang.RuntimeException: java.lang.NullPointerException
[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R at com.ibm.io.async.ResultHandler.runEventProcessingL oop(ResultHandler.java:793)
[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R at com.ibm.io.async.ResultHandler$2.run(ResultHandler .java:873)
[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.j ava:1473)
[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R Caused by: java.lang.NullPointerException
at com.ibm.io.async.AsyncFuture.completed(AsyncFuture .java:111)
at com.ibm.io.async.ResultHandler.complete(ResultHand ler.java:195)
at com.ibm.io.async.ResultHandler.runEventProcessingL oop(ResultHandler.java:743)
at com.ibm.io.async.ResultHandler$2.run(ResultHandler .java:873)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.j ava:1473)

[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R at com.ibm.io.async.AsyncFuture.completed(AsyncFuture .java:111)
[9/17/08 16:44:05:508 CDT] 0000003a SystemErr R at com.ibm.io.async.ResultHandler.complete(ResultHand ler.java:195)
[9/17/08 16:44:05:524 CDT] 0000003a SystemErr R at com.ibm.io.async.ResultHandler.runEventProcessingL oop(ResultHandler.java:743)
[9/17/08 16:44:05:524 CDT] 0000003a SystemErr R ... 2 more

Or:
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R Exception in thread "WebContainer : 13" java.lang.NullPointerException
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.tcp.channel.impl.NioSocketIOChannel.attemptWriteToSocketUsingNIO(NioSocketIOChannel.java:160)
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.tcp.channel.impl.SocketIOChannel.attemptWriteToSocket(SocketIOChannel.java:763)
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.tcp.channel.impl.WorkQueueManager.attemptIO(WorkQueueManager.java:628)
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.tcp.channel.impl.WorkQueueManager.workerRun(WorkQueueManager.java:979)
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.tcp.channel.impl.WorkQueueManager$Worker.run(WorkQueueManager.java:1064)
[24.10.08 12:00:47:493 CEST] 000000b5 SystemErr R at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1473)

To fix this exceptions see the link above or navigate to Application Servers > <your_app_server> > Web container > Custom properties > New

Name: com.ibm.ws.webcontainer.channelwritetype
Value: sync

Restart your app server