Samuel,
Not sure about the requests that are marked as read. That's definitely not normal behavior. Please test more and let us know if it happens again, and feel free to use our test page to see if you see the same problem:
www.sourcecoast.com/jfbconnect/features/joomla-facebook-request
For the requests that stopped working, are you saying while you were sending admin requests, the page froze or otherwise stopped sending requests part way through? Unfortunately, if that's the case, JFBConnect doesn't currently have a way to resume sending requests. We do send requests in order of the User Map table. You may need to page through the User Map table, find the last user that a request was recorded too, and then manually send invitations to the rest. Setting the list count to 100 and using the "Check All" box at the top should make that relatively painless, but will definitely still take some time. We have plans to look into a resume functionality for problems like that, but in almost 6 months, you're the first user to mention having that problem.
Hope that explains,
Alex