Unreachable warning - Google Webmaster Errors

Those errors are a consequence of Google crawling Javascript links. We insert the logout URL that a user should go to when they click the Logout button in a Javascript tag. Facebook recently began crawling these links and it can cause the 404 errors you show if:
1) You have the Logout Redirection link set to a page that doesn't exists
2) You have JFBConnect configured to leave the user on the same page they logged out from. If that content is for registered users only, that can cause a redirection that Google doesn't like.

For our 4.0 release (coming up in July), we'll be working on some fixes to prevent these errors from showing up in the webmaster tools. However, please note that they are not legitimate problems that end-users will run into, just Google while it's indexing. It's not fun to see, and we do want to fix them, but should not affect normal navigation of your site.

Hope that helps explain,
Alex

Keith,
Actually have a question for you about the unreachable pages, as well as a suggestion if you want to stop the problem right now, before our anticipated fix. For the page you mention above, it's a JFBConnect page, which is meant to redirect the user to the proper logout page. In that case though, the page it's trying to redirect the user to was:
/milonga/groups/viewdiscussions.html?groupid=6

That's meant for a JomSocial group discussion page. Can you check if the group id of 6 actually still exists? If not, was it deleted? That would explain why the error is a 404 and would happen to any page that linked to that, now non-existent page. Also, was this page ever set as the logout redirection page in the JFBConnect configuration area?

A suggestion to fix the problem right now would be to set a Logout Redirection in the JFBConnect page. Set it to a publicly viewable page, and that way, when a user logs out, they will always go to a public page. This will also prevent Google from seeing the redirections to pages it may not be able to access.

Finally, for the unreachable errors, make sure your Facebook application is setup correctly with the following Site and Domain settings:
Site URL: www.tangobeat.com/
Base/Domain URL: tagobeat.com
Additionally, can you check if the only pages you're seeing those issues on are pages that are marked as registered or Special, or if you're seeing them on public pages as well?

Thanks, and hope this helps!
Alex