CB 1.7 RC
Please upgrade to CB 1.7.1, your install is out of date; RC is not meant for production sites.
When users of PlanB log in they very very often get the message, "you are not allowed to few the ressource"
Means the page they're being redirected to they don't have access to. This could be due to missing or wrong Itemid in the URL for example.
Please ensure the URL you're supplying for redirect is the one provided for you when editing the userlist in CB > Userlist Management. Starting with index.php and not live site.