I'm not sure why the SCLogin module wouldn't be logging you out. Can you check the "Logout of Joomla Only" setting in the JFBConnect configuration area? Try setting it to "Yes".
Also, from the post below, I recommended using the other Login module you have on the site and just adding the Login with FB button to it. If you decide to do that, it may be a solution to this problem as well:
www.sourcecoast.com/forums/jfbconnect/jf...automatically#p32023
Hope that helps,
Alex