Error message: "Your site was unable to contact the Apache Solr server."

Hi,

I've properly installed Solr 3.5.0 on Tomcat 7 in a CentOS 6 distribution, configuring Solr to run with a single core (standard method).
I've installed Drupal 7.12 and the module Apache Solr Search Integration (7.x-1.0-beta16), replacing the files schema.xml, solrconfig.xml and protwords.txt in the conf Solr directory with those that come with the module.

So, I've acces to:

http://localhost:8080/solr/

and to:

http://localhost:8080/solr/admin/

with no errors. All works fine.

But when I try to configure the settings in the Drupal site (admin/config/search/apachesolr/settings/solr/edit), from the same computer and browser, I can't connect with the Solr server (the error message is "Your site was unable to contact the Apache Solr server.").

In the filed "Solr server URL" I've tried with:

http://localhost:8080/solr/
http://localhost:8080/solr
http://localhost:8080/solr/admin
http://localhost:8080/solr/admin/

but I obtain the same error message with all of them.

Just in case..., installing Tomcat 7 I had changed the iptables:

[root@15900696 ~]# /sbin/iptables -I INPUT 1 -p tcp --dport 8080 -j ACCEPT
[root@15900696 ~]# /sbin/iptables -I INPUT 1 -p tcp --dport 80 -j ACCEPT
[root@15900696 ~]# iptables -t nat -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 8080
[root@15900696 ~]# iptables -t nat -A PREROUTING -p udp -m udp --dport 80 -j REDIRECT --to-ports 8080
[root@15900696 ~]# /sbin/service iptables save
[root@15900696 ~]# service iptables restart

I've had the same problem with a Solr multicore installation (http://drupal.org/node/1445836).

Please, any idea?

Thanks!!