Thought I would post this for others to see what the problem was. Turned out the 1 plugin I would have thought was solid (taking the programmer into consideration) the SEO Canonicalisation Plugin plugin as can be downloaded from the JED and gets great ratings was the culprit. In disabling it login works, re-enabling login doesn't, so until Sam Moffatt the programmer replies to my contact or updates it to work with CB login, it has been uninstalled.