Ok, well switching to TCP did the trick, however, we still could not use MS NLB because it has some other requirements we were not able to overcome. MS NLB requires an ARP address statically added to the router/switch in the mode we were running it in, which is not the preferred method in the environment we were deploying in. So, instead, we have switched to a HW based NLB solution. I then switched everything back to UDP multicasting, and all seems happy...so far ;) Still, keep in mind, there is some strange incompatibility between MS NLB and UDP multicast JBOSS clusters. Just my 2 cents ;) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4029550#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...