trans-id enabled not working?

I am experiencing a problem with NN6.2. When I link to a url from a popup the session id is not being appended to the url. The destination page check session variables and redirects to an error page. If I add the query portion "?PHPSESSID=,?php session_id() ?>" to the link string it works. However, if I use Omniweb or IE 5.2 I do doesn't redirect and session variables appear in the page as expected. I do notice that sometimes the ID string is appended and sometines it isn't. Each page's first line is session_start(). Are there some rules as to when the url rewriter intercepts the call? Jerry Artman interactivemedianet.com