NIS 21.0.1.3 update screwed up 3 networked computers' (2 XP and 1 Win 7) abilities to see and work w/ one another, and also screwed up abilities of XPs to receive downloaded temperatures in Weather Channel apps. Finally found problem w/ SMART firewall in NIS re Weather Channel app (had to change Program Rules on both XPs to ALLOW instead of BLOCK with respect to Weather Channel apps). After about a week of numerous addl. changes, resettings, reboots, and cursing, finally got computers networked and working together again, but not sure quite how after all the changes. I think that issue was also related to the SMART firewall. Little or no documentation or help from Norton in finding solutions. Something similar seems to arise with every significant update.