sorry, forgot to update the post...problem solved!

turns out that the fix below (line 900, fixing cookie name) works for IE. other browsers, however, require a change in the setcookie() function around lines 696 and again 720.

you will see
setcookie( $sessionCookieName, '-', false, '/' );
twice in that area (the two are slightly different but because the "-" is only on the first one, a variable takes its place on the second one). change both so that you add a variable at the end that is '.example.com.'

they'll look something like:
setcookie( $sessionCookieName, '-', false, '/' , '.example.com' );



The good news is, do both fixes (the IE version and this other one) and you'll be set across browswers! I've tested in IE5.5, IE6, IE7, FF3, Safari3, and Opera. Hope this helps someone else!