Losing Session Variable in IE Only?

I am having the strangest problem and I'm not sure there is anybody on this planet smart enough to figure it out.... I have a PHP application that I was running and testing under an existing URL, but by adding a port number to go to a different directory. Like this, http://www.investmentteams.com:3333 It worked fine. I registered a domain name for it, got DNS set up, went to the index.php page, did the login, but then when it transferred to the next page, all the session variables were gone and this really makes the whole thing unusable. Here are the extenuating circumstances: It works fine in Netscape. It works fine in IE 5-point-something at work. Other websites using session variables (like www.investmentteams.com) work fine in IE6 at home. Oddly enough, the new URL is www.problemrpts.com , but if I cannot login I cannot enter a problem report!!!! Any guesses on this one? TIA