This is an old topic, but for those wondering, this is best done via the registration queue.
From there you can see all other accounts with matching IPs and approve/deny as needed.
@kevin Going backwards is very rarely possible. For example, you can't downgrade from 0.6.x to 0.5.x as the DB schema is different. Not sure if that's the case with 0.6.1 to 0.6.x stable, but you can try doing
git checkout v0.6.x
Or latest master may even have fixed whatever issues you had. I'm running it without issues.