1. JomSocial also has its own plugin 'System - Jomsocial Redirect' which might be trying to override these values. You can either disable this plugin since you're using SCLogin, or set the values appropriately for Login, Login Failed, and Logout in that plugin and re-try.
2. If #1 does not work, then I would suggest looking into any SEF extensions or caching that you have enabled on your site. These two areas would be the next common causes of behavior you're seeing.
-Melissa