Odds are, it's a problem with Javascript code on Ebay. That's what I'm guessing.

Netscape 4.x has always had problems with its javascript runtime interpreter, causing certain bits of javascript code to crash the browser. I'm guessing they made a little change to some of the code on ebay and didn't regression test it with all of the various netscape builds.

I'm not sure e-bay is even usable at all with Javascript turned off, but I know that Netscape can disable javascript in its configuration menus. Give that a try...