You didn't mention which version of Netscape you are running. Also, are you using the same dialup connection for both Netscape and Explorer?

I'm running the beta version of Netscape 4.5 and IE4 under both win98 and winNT. (both using the same connection to the same ISP under Win98.) When I originally created the dialup connection under win98, it installed NetBEUI, IPX/SPX, and TCP/IP as acceptable server types. I had to remove all but TCP/IP before Netscape would behave correctly.