How did you determine that the app server is sending the requests twice? Personally, I have never experienced this behavior.
using TCPMON I can see that the server receives twice all the client requests.
The first immediately and the second after few seconds.
It is very strange, because the HTML code is quite simple and with other AppServers like Websphere the problem doesn't exists.
So I think about some possible configuration problem with JBOSS.
if you have any ideas..
now the problem is more restricted.
Only the requests sent from a client that is on the same machine of the JBOSS AppServer are duplicated (so calls to localhost).
If the client and the server are on different machines (or the client invokes the server by its http://ipaddress:port/url instead of http://localhost:8080/url) the problem does not exists.
So I think that, as you suppose, the problem could be related to some network issues.