User Role Unable to be defined and signup page errors

Hello,
I have recently had problems with a few things at our site
* People trying to register are unable to do so, as the page simply refreshes each time they hit register now with no explanation as to why.
** When I create a user or if someone is a previous user their role has been changed to editor or admin and though it says they are in the backend of the main admin blog , they don't get the main blog in their drop down list of blogs they can contribute to or edit.