I'm having some sessions problems after my ISP moved my site to a new server, supposedly setup the same. The problem appears to be browser-specific as well, which I don't quite understand.

First, my site uses sessions to login, this has been broken since they moved the site.

My ISP has set up a test page at http://launchcomplex.com/loggedin_test1.php. When I hit this page in IE 6 (where it sets some session vars) and then hit the "header redirect" button, sessions seem to work fine. If I try it in Firefox/Opera, I get a new session id on the redirected page. My ISP reports sessions are working for IE as well, though I imagine they're using IE7 or perhaps even 8.

Everything was working fine on my site before my ISP moved it and while they've been very helpful in responding, they're at a loss as to why it's broken. A couple of other of my sites with them were broken along with the move, but they have been resolved by server tweaks...Does anyone have any ideas what's going on?