I had a similar problem and resolved it by changing the “?” to a “&” in the URL. When you access the page from the admin menu, your custom parameter is actually the SECOND variable that gets passed, so you would use the “&” to append it to the URL instead of the “?”
WRONG:
http://www.mysite.com/wp-admin/admin.php?page=member?id=0
RIGHT:
http://www.mysite.com/wp-admin/admin.php?page=member&id=0
