Yorai,
We've already announced that JLinked will be fully integrated into JFBConnect with the next major release (in early 2014). At that point, JLinked will be discontinued as a standalone product. That will make development, support, and setup easier for everyone, and we'll be excited when it's all ready. Feel free to keep an eye on our blog for such announcements!
Now, as to your problem, I'm honestly not sure what's happening. But here are a few things to check:
1) Make sure you're on the latest release of JLinked.
2) After you install JLinked, install JFBConnect again. Your settings in both will remain. JFBConnect has a newer version of our "SourceCoast Library". If you install JLinked 2nd, you'll actually downgrade the library and that could cause some of your issues.
3) For the "the email adress is already registered", try enabling the "Automatically connect users by email". That should link the 2 accounts automatically if the Joomla and LinkedIn email are the same.
As for the "JLinked User", do you just mean that a user shows up in the JLinked -> Usermap area? That area simply means there is a 'connection' between LinkedIn and a Joomla user on your site. Each row isn't necessarily a whole new user. So, it's possible the connection was made properly if there is a row within the Usermap area. You'd need to check the Joomla user that was linked to that account.
I hope that all helps explain, but if not, or you have any other questions, just let me know.
Thanks,
Alex