A few days ago Oracle released a new version of Oracle SQL Developer 3.2.
The patch contains bug fixes and introduces some new features, but it also carries some behavioural changes. One caught me and I think many other people will hit the same issue.
The connection names in SQL Developer can't contain spaces anymore as it could do before version 3.2.1. Your current connections which contain spaces will still work, but you can't save them anymore incase you wanted to make a change. Below is an example of the connection with and without space.
I would have preferred connection names would still allow spaces, but it is what it is now, so following steps I found best to migrate my connection names to the new naming rules in SQL Dev 3.2.1:
-) right click on the connection name and click on Rename Connection
-) change all the spaces to underscores or take them off where possible
You could keep the names as they are for now (with spaces), but the issue I found was that if you add a new connection the order is not correct anymore, as first you will see all underscores and only after the the (old) connections with spaces.
Note that if you click on the connection and change it, and change the name at that time, it will create a new connection with the new name, that is why before I find it easier to just do a bulk rename of all my connection names.
I would definitely upgrade to the latest version of SQL Developer as you get more features with every new release and development becomes faster and easier.