I got to poking around in the "trust settings" for Netscape 8.0 and noticed that if the "display like MSIE" selection was on the various cookie options greyed out, but when "display like FireFox" was selected the cookie options we available. For some reason eBay was defaulting to the MSIE view, which was doing something funky with the cookies. Hopefully the changes I made will "stick" ... because right now I can open tabs up from my main eBay screen all I want, and it's not bugging me for a new sign-in!
WHEEEEEE!
It's amazing that MSIE found a way to irritate me without even using it!