Usually stuff like this is the fault of the computer at hand. In IE turn on cookie prompting and see if you get the prompt. Also clear out all of your cookies and try that again.

What steps did you come to to conclude that it isn't working with lynx and ie6? Not in the cookie dir? no prompt? etc. Have your page spit out all of the valid cookies for the domain. Is any fraction of it in there? Since you can't have IE5 and IE6 on the same machine at the same time, it strikes me that they may be separate machines. Also shift-refresh in IE to bypass the local cache (and you may want to add a quick localtime() statement to your page to make sure that it's changing. CGI debugging is kind of icky, but good luck with it.

    --jb