NIS and network internet connection

Ive recently connected both my computers on my network without a problem, untill i installed norton internet security 2003. now it only lets the host computer browse the internet, whereas both could before hand. file sharing and printer sharing still work fine and ive tried disabling firewalls on both computers without success. ive had this problem with my old computer, but cannot remember how i got them working again. any help would be much appreciated!