Shared Internet connection via router

I have recently added a 4-port cable/dsl router to connect 2 PCs to share internet connection. PC1 connects to the internet directly via a cable modem and its operating system is Win 98. PC2’s operating system is Win XP. The LAN setup was a success,however, the internet share connection has been working sporadically. Everytime I power up the PC or PCs I get a DNS error msg on PC1 and no internet connection at all on PC2. To correct the problems, I have to reset the router and start the set up all over again. What could be the problem?