Remote app stops connecting to iTunes

I have set up my iTunes to be controlled by my iOS devices (2 iPhones, and 2 iPads). The remote on one of the iPads stop connecting. I check the settings on the other iPad and the iPhones. Both work initially until I go to the library selection screen. Now all 4 devices stop connecting. The message on the iPad after I turn on the Home sharing is "Turn on Sharing on your computer using account xxxx. I have turned off and back on the iPhones, iPads, computer and routers, nothing helps. I even uninstalled and re-installed iTunes and the Remote apps. Log out and back on the Home sharing on all devices. I turn off the Norton firewall briefly to test it. I also follow the trouble shooting, and nothing helps. Any suggestion? Thanks

My system is Window Vista.