I am wondering what OS you using. I have the similar problem as below. It happened on both JBoss3.0.4 with Jetty and JBoss3.2.3 with Tomcat.
I am using Sun Solaris 2.8
Sorry for late reply, I was out-of-work for the past 2 days.
Have you sorted the issue? Any clues would be very helpful.
Check if you are mixing http-post and http-get.
I had the same problem and it turned out to be from the following:
form action="?id=1" method="post"
fixed it with making id as a hidden field.