Don't think moodle caches user info ... it does keep track of sessions. Is your site using DB for sessions or files?
Purge caches ... if using files for sessions, manually remove all session files in moodledata/sessions/ - that will force all users out and they will have to login again doing that.
Still ... the screen shot ... third line down said user with ID 1 (the guest user) *CREATED* user id 246. Didn't think that possible unless user ID 1 has the ability to create.
Accounts set to manual are using moodle's own authentication ... openID the user info is coming from outside of Moodle.
So what does user id 246 look like at the other end ... then openid end?