Every evening I usually spend some time here on iboats and other web sites that may strike my fancy rather than watching TV. As I bounce around I usually listen to web radio (great jazz - http://www.kplu.org/whatson/indexlisten.cgi) <br /><br />Once or twice every evening I hear this rather loud Knock-Knock-Knock sound coming from my sound system. Am I going nuts?? <br /><br />Is it coming from iboats?? Web radio?? A friendly virus (I have both Norton & use a firewall)??<br /><br />Any ideas?