42 - Failed to update contact: COM_CONTACT_WARNING_SAME_NAME

I'm assuming you're talking about the "User - Contact Creator" plugin? We haven't tested with that before, but we can now. We definitely changed the general flow of the user creation for Facebook users, to generally improve compatibility with a lot of extensions, it's possible it's caused some other minor conflicts where things worked before.

As for some things to test, please:
1) Try setting the Contact Creator plugin to be ordered last (highest) after the Joomla - User plugin and JFBConnect - User plugins
2) When you installed new, are you sure there was no data previously in the database that you're using? If there was any lingering data, or partial remnants of users past, that could easily cause the problem.

Thanks,
Alex

If you're using JomSocial, I wouldn't recommend that plugin it all. That plugin simply inserts the user into the Contacts component that comes with Joomla. JomSocial has much more robust user profile and display capabilities, and doesn't have the issue you're mentioning. That plugin is also disabled by default, so it's not something that Joomla even recommends you enable on all sites.

My guess is that when you delete the user, it's not deleting them from the Contacts Component, so when you register again, it's trying to create a user with the same username in Contacts, which is then causing the error your seeing. Can't guarantee it, but if you don't plan on using it, we likely won't be investigating right away either

Good luck,
Alex