I found serveral IllegalStateException Exception in the logs:
[#|2009-01-28T14:10:16.050+0100|SEVERE|sun-appserver2.1|javax.enterprise.system.container.web|_ThreadID=26;_ThreadName=httpSSLWorkerThread-80-53;_RequestID=871b8812-7bc5-4ed7-85f1-ea48f760b51e;|WEB0777: Unblocking keep-alive exception
java.lang.IllegalStateException: PWC4662: Request header is too large
at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:740)
at org.apache.coyote.http11.InternalInputBuffer.parseHeader(InternalInputBuffer.java:657)
at org.apache.coyote.http11.InternalInputBuffer.parseHeaders(InternalInputBuffer.java:543)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.parseRequest(DefaultProcessorTask.java:712)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:577)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:831)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214)
at com.sun.enterprise.web.portunif.PortUnificationPipeline$PUTask.doTask(PortUnificationPipeline.java:380)
at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265)
at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)
|#]
Does anybody know configuration changes to fix this?